query: What is the theory behind Rick Van Ness's risk calculation in the video about diversification?

positive: "He's calculating portfolio variance. The general formula for the variance of a portfolio composed of two securities looks like this:  where w_a and w_b are the weights of each stock in the portfolio and the sigmas represent the standard deviation/risk of each asset or portfolio.  In the case of perfect positive or negative correlation, applying some algebra to the formula relating covariance to the correlation coefficient (rho, the Greek letter that looks like ""p""):  tells us that the covariance we need in the original formula is simply the product of the standard deviations and the correlation coefficient (-1 in this case).  Combining that result with our original formula yields this calculation:  Technically we've calculated the portfolio's variance and not it's standard deviation/risk, but since the square root of 0 is still 0, that doesn't matter. The Wikipedia article on Modern Portfolio Theory has a section that describes the mathematical methods I used above. The entire article is worth a read, however."

positive: "John Bensin's answer covers the math, but I like the plain-English examples of the theory from William Bernstein's fine book, The Intelligent Asset Allocator.  At the author's web site, you can find the complete chapter 1 and chapter 2, though not chapter 3, which is the one with the ""multiple coin toss"" portfolio example I want to highlight. I'll summarize Bernstein's multiple coin toss example here with some excerpts from the book.  (Another top user, @JoeTaxpayer, has also written about the coin flip on his blog, also mentioning Bernstein's book.) Bernstein begins Chapter 1 by describing an offer from a fictitious ""Uncle Fred"": Imagine that you work for your rich but eccentric Uncle Fred. [...] he   decides to let you in on the company pension plan. [...] you must pick   ahead of time one of two investment choices for the duration of your   employment: Certificates of deposit with a 3% annualized rate of return, or, A most peculiar option: At the end of each year Uncle Fred flips a coin. Heads you receive a 30% investment return for that year, tails a   minus 10% (loss) for the year. This will be hereafter referred to as   ""Uncle Fred’s coin toss,"" or simply, the ""coin toss."" In effect, choosing option 2 results in a higher expected return than option 1, but it is certainly riskier, having a high standard deviation and being especially prone to a series of bad tosses.  Chapters 1 and 2 continue to expand on the idea of risk, and take a look at various assets/markets over time.  Chapter 3 then begins by introducing the multiple coin toss example: Time passes. You have spent several more years in the employ of your   Uncle Fred, and have truly grown to dread the annual coin-toss   sessions. [...] He makes you another offer. At the end of each year,   he will divide your pension account into two equal parts and conduct a   separate coin toss for each half [...] there are four possible   outcomes [...]: [...]   Being handy with numbers, you calculate that your annualized return   for this two-coin-toss sequence is 9.08%, which is nearly a full   percentage point higher than your previous expected return of 8.17%   with only one coin toss. Even more amazingly, you realize that your   risk has been reduced — with the addition of two returns at the   mean of 10%, your calculated standard deviation is now only 14.14%, as   opposed to 20% for the single coin toss. [...] Dividing your portfolio between assets with uncorrelated results increases return while decreasing risk. [...]   If the second coin toss were perfectly inversely correlated   with the first and always gave the opposite result [hence, outcomes   1 and 4 above never occurring], then our return would always be 10%.   In this case, we would have a 10% annualized long-term return with zero risk! I hope that summarizes the example well.  Of course, in the real world, one of the tricks to building a good portfolio is finding assets that aren't well-correlated, and if you're interested in more on the subject I suggest you check out his books (including The Four Pillars of Investing) and read more about Modern Portfolio Theory (MPT)."

positive: "The calculation and theory are explained in the other answers, but it should be pointed out that the video is the equivalent of watching a magic trick.  The secret is: ""Stock A and B are perfectly negatively correlated.""  The video glasses over that fact that without that fact the risk doesn't drop to zero. The rule is that true diversification does decrease risk. That is why you are advised to spread year investments across small-cap, large-cap, bonds, international, commodities, real estate. Getting two S&P 500 indexes isn't diversification.  Your mix of investments will still have risk, because return and risk are backward calculations, not a guarantee of future performance. Changes that were not anticipated will change future performance. What kind of changes: technology, outsourcing, currency, political, scandal."

negative: "When you invest in a single index/security, you are completely exposed to the risk of that security. Diversification means spreading the investments so the losses on one side can be compensated by the gains on the other side. What you are talking about is one thing called ""risk apettite"", more formally known as Risk Tolerance: Risk tolerance is the degree of variability in investment returns that an investor is willing to withstand. (emphasis added) This means that you are willing to accept some losses in order to get a potential bigger return. Fidelity has this graph:  As you can see in the table above, the higher the risk tolerance, the bigger the difference between the best and worst values. That is the variability. The right-most pie can be one example of an agressive diversified portfolio. But this does not mean you should go and buy exactly that security compostion. High-risk means playing with fire. Unless you are a professional stuntman, playing with fire usually leaves people burnt. In a financial context this usually means the money is gone. Recommended Reading: Investopedia; Risk and Diversification: The Risk-Reward Tradeoff Investopedia; How to construct a High Risk portfolio Fidelity: Guide to Diversification KPMG: Understanding and articulating Risk Appetite (pdf)"

negative: "In theory, the idea is that diversified assets will perform differently in different circumstances, spreading your risk around. Whether that still functions in practice is a decent question, as the ""truth"" of most probability based arguments for diversification rely on the different assets being at least somewhat uncorrelated. This article suggests that might not be true. Specifically: The correlations we note among industry sectors are profoundly and dysfunctionally high. and  Gold and silver traders have gotten too used to the negative correlation trade with stocks. This is, in fact, an unusual relationship for precious metals tostocks. The correlation should actually be zero."

negative: if I have a asset A with expected return of 100% and risk(measured by standard deviation) 1%, and asset B with expected return of 1% and risk 100%, would it be rational to put asset B into the portfolio ? No, because Modern Portfolio Theory would say that if there is another asset (B2) with the same (or higher) return but less risk (which you already have in asset A), you should invest in that. If those are the only two assets you can choose from, you would invest completely in Asset A. The point of diversification is that, so long as two assets aren't perfectly positively correlated (meaning that if one moves up the other always moves up), then losses in one asset will sometimes be offset by gains in another, reducing the overall risk.

negative: "Diversification is extremely important and the one true ""Free Lunch"" of investing, meaning it can provide both greater returns and less risk than a portfolio that is not diversified. The reason people say otherwise is because they are talking about ""true"" portfolio diversification, which cannot be achieved by simply spreading money across stocks. To truly diversify a portfolio it must be diversified across multiple, unrelated ""Return Drivers."" I describe this throughout my best-selling book and am pleased to provide complimentary links to the following two chapters, where I discuss the lack of diversification from spreading money solely across stocks (including correlation tables), as well as the benefits of true portfolio diversification: Jackass Investing - Myth #8: Trading is Gambling – Investing is Safer Jackass Investing - Myth #20: There is No Free Lunch"

negative: You're missing the concept of systemic risk, which is the risk of the entire market or an entire asset class. Diversification is about achieving a balance between risk and return that's appropriate for you. Your investment in Vanguard's fund, although diversified between many public companies, is still restricted to one asset class in one country. Yes, you lower your risk by investing in all of these companies, but you don't erase it entirely.  Clearly, there is still risk, despite your diversification. You may decide that you want other investments or a different asset allocation that reduce the overall risk of your portfolio. Over the long run, you may earn a high level of return, but never forget that there is still risk involved. bonds seem pretty worthless, at least until I retire According to your profile, you're about my age. Our cohort will probably begin retiring sometime around 2050 or later, and no one knows what the bond market will look like over the next 40 years. We may have forecasts for the next few years, but not for almost four decades. Writing off an entire asset class for almost four decades doesn't seem like a good idea. Also, bonds are like equity, and all other asset classes, in that there are different levels of risk within the asset class too. When calculating the overall risk/return profile of my portfolio, I certainly don't consider Treasuries as the same risk level as corporate bonds or high-yield (or junk) bonds from abroad.  Depending on your risk preferences, you may find that an asset allocation that includes US and/or international bonds/fixed-income, international equities, real-estate, and cash (to make rebalancing your asset allocation easier) reduces your risk to levels you're willing to tolerate, while still allowing you to achieve returns during periods where one asset class, e.g. equities, is losing value or performing below your expectations.

negative: "Taking examples from this loosely Googled page: http://www.fundlibrary.com/features/columns/page.asp?id=14406 If you find, or calculate, the standard deviation (volatility) of the returns from your various investment classes you will find they range from low-risk (low volatility), such as Cash, to high-risk (high volatility), such as Strategic Growth.  The risk rating (volatility) is a good indicator of how reactive to market conditions your investment is likely to be.  As you can see below, from mid-2010 to mid-2011 the High Risk index performed really well, but it was also most reactive when the market subsequently turned down.  The medium risk indices performed the best over the chart period, 2010 to 2013, but it could have turned out different.  Generally, you choose your investment according to your ""risk appetite"" - how much you're willing to risk.  You might play safe with, say, 30% cash, 60% medium risk, 10% high risk.  (Then again, are you paying someone to manage cash, which you might be able to do for free in a bank?) Assuming, for a moment, European (3.) and Intnl Equity Tracker (9.) had the same medium risk profile, then holding 50% & 50% would also add some currency diversification, which is usually advisable.  However, the main choice is down to risk appetite. To address your specific question: ""my main interest for now is between Stockmarket Growth and Strategic Growth"", first thing to do is check their volatilities. For a further level of sophistication you can check how they are correlated against each other.  If they are inversely correlated, i.e. one goes up when the other goes down, then holding some of each could be a good diversification. FYI: An Introduction to Investment Theory The historical returns are important too, but the investment classes your pension fund is offering will probably be reasonably aligned on a risk-return basis.  You should check though.  I.e. do they line up on a plot of 3 year Return vs Volatility? e.g. the line through SA Cash - SA Bonds - Vol Target 20 - SA Equity.  Source"

negative: "Okay, yes! That would seem to make sense. So something like a Dupire local vol model.   In the context of term structure modelling, you can also incorporate a volatility surface into the pricing of European and even exotic options (e.g. through a SABR or an LMM-SABR for exotics), which I suppose means by your criteria there are actually varying degree of ""arbitrage free-ness"" when it comes to picking a model. By that I mean there are varying degrees of what your model takes as ""given"". If it takes the market price of risk as given, it's an equilibrium model. If it takes the observed term structure as given, it's an arbitrage free model. If it takes the volatility structure as given, it's something else.  Nawalkha, Beliaeva and Soto wrote a paper called ""A New Taxonomy of the Dynamic Term Structure Models"" in the Journal of Investment Management that basically coincides with what we're saying.  So yes, it sounds right to me."

negative: "While it's definitely possible (and likely?) that a diversified portfolio generates higher returns than the S&P 500, that's not the main reason why you diversify. Diversification reduces risk.  Modern portfolio theory suggests that you should maximize return while reducing risk, instead of blindly chasing the highest returns. Think about it this way--say the average return is 11% for large cap US stocks (the S&P 500), and it's 10% for a diversified portfolio (say, 6-8 asset classes). The large cap only portfolio has a 10% chance of losing 30% in a given year, while the diversified portfolio has a 1% chance of losing 30% in a year. For the vast majority of investors, it's worth the 1% annual gap in expected return to greatly reduce their risk exposure. Of course, I just made those numbers up. Read what finance professors have written for the ""data and proof"". But modern portfolio theory is believed by a lot of investors and other finance experts. There are a ton of studies (and therefore data) on MPT--including many that contradict it."

negative: "There are some good answers about the benefits of diversification, but I'm going to go into what is going on mathematically with what you are attempting. I was always under the assumption that as long as two securities are less than perfectly correlated (i.e. 1), that the standard deviation/risk would be less than if I had put 100% into either of the securities. While there does exist a minimum variance portfolio that is a combination of the two with lower vol than 100% of either individually, this portfolio is not necessarily the portfolio with highest utility under your metric.  Your metric includes returns not just volatility/variance so the different returns bias the result away from the min-vol portfolio. Using the utility function: E[x] - .5*A*sig^2 results in the highest utility of 100% VTSAX. So here the Sharpe ratio (risk adjusted return) of the U.S. portfolio is so much higher than the international portfolio over the period tracked that the loss of returns from adding more international stocks outweigh the lower risk that you would get from both just adding the lower vol international stocks and the diversification effects from having a correlation less than one. The key point in the above is ""over the period tracked"".  When you do this type of analysis you implicitly assume that the returns/risk observed in the past will be similar to the returns/risk in the future.   Certainly, if you had invested 100% in the U.S. recently you would have done better than investing in a mix of US/Intl.  However, while the risk and correlations of assets can be (somewhat) stable over time relative returns can vary wildly! This uncertainty of future returns is why most people use a diversified portfolio of assets.  What is the exact right amount is a very hard question though."

negative: "Diversification tends to protect you from big losses. But it also tends to ""protect"" you from big gains. In any industry, some companies provide good products and services and prosper while others have problems and fail. (Or maybe the winners are just lucky or they paid off the right politicians, whatever, not the point here.) If you put all your money in one stock and they do well, you could make a bundle. But if you pick a loser, you could lose your entire investment. If you buy a little stock in each of many companies, then some will go up and some will go down, and your returns will be an average of how everyone in the industry is doing. Suppose I offered to bet you a large sum of money that if I roll a die, it will come up 6. You might be reluctant to take that bet, because you can't predict what number will come up on one roll of a die. But suppose I offered to bet you a large sum of money that a die will come up 6, 100 times in a row. You might well take that bet, because the chance that it will turn up 6 time after time after time is very low. You reduce risk by spreading your bets. Anyone who's bought stock has surely had times when he said, ""Oh man! If only I'd bought X ten years ago I'd be a millionaire now!"" But quite a few have also said, ""If only I'd sold X ten years ago I wouldn't have lost all this money!""  I recently bought a stock a stock that within a few months rose to 10 times what I paid for it ... and then a few months later the company went bankrupt and the stock was worth nothing. I knew the company was on a roller coaster when I bought the stock, I was gambling that they'd pull through and I'd make money. I guessed wrong. Fortunately I gambled an amount that I was willing to lose."

negative: At its simplest level it's an application of basic statistics/probability: Suppose you have n independent and identically distributed assets with the return on asset i denoted R_i which has mean m and variance s^2 (same for all assets). You can easily weaken these assumptions but I make them to simplify the exposition  [Square brackets show a numerical example with n=20, m=8%, s=2%] if you invest in one of these assets you expect to get a return of m [8%] with standard deviation s [2%] (so you expect with probability 95% (approx) to get a return between m-2*s and m+2*s.  [between 4% and 12%] Now suppose you split your money equally among the n-assets.  Your return is now R = (1/n)\Sum{i=1}^n R_i your expected return is  E(R) = (1/n)\Sum{i=1}^n E(R_i) = (1/n)\Sum{i=1}^n m = m   [8%] the variance of your return is  Var(R) = Var( (1/n)\Sum{i=1}^n R_i )       = (1/n^2)\Sum{i=1}^n Var(R_i) = n * s^2 / n^2) = s^2/n    So, the standard deviation is SD(R) = Sqrt(V(R)) = s/Sqrt(n) [2%/Sqrt(20) = 0.44%] Now, with 95% probability we get a return between E(R)-2*SD(R) and E(R)+2*SD(R) [between 7.12% and 8.88%].  This interval is smaller than when we invested in the single asset, so in effect with this portfolio we are achieving the same return m [8%] but with lower variance (risk) [0.44% instead of 2%].  This is the result of diversification.     You can assume the assets are not independent (and most book expositions of this topic do indeed do that). In that case the calculation is modified because the variance of the portfolio now depends on the correlation between returns, as does the reduction in variance caused by the diversification.  If assets are negatively correlated the result of the diversification will be more reduction in risk and vice versa.   You can also assume the assets are not identically distributed and the above analysis does not change too much.   You might look for some references on CAPM (Capital Asset Pricing Model) or portfolio theory but broadly these are based on what I have described above - finding the portfolio with minimum variance for a given return by investing proportionally in treasury bonds and risky assets.

negative: If you have 100% of your money in one security that is inherently more risky than splitting your money 50/50 between two securities, regardless of the purported riskiness of the two securities. The calculations people use to justify their particular breed of diversification may carry some assumptions related risk/reward calculations.  But these particular justifications don't change the fact that spreading your money across different assets protects your money from value variances of the individual assets.  Splitting your $100 between Apple and Microsoft stock is probably less valuable (less well diversified) than splitting your money between Apple and Whole Foods stock but either way you're carrying less risk than putting all $100 in to Apple stock regardless of the assumed rates of return for any of these companies stock specifically. Edit: I'm sure the downvotes are because I didn't make a big deal about correlation and measuring correlation and standard deviations of returns and detailed portfolio theory.  Measuring efficacy and justifying your particular allocations (that generally uses data from the past to project the future) is all well and good.  Fact of the matter is, if you have 100% of your money in stock that's more stock risk than 25% in cash, 25% in bonds and 50% in stock would be because now you're in different asset classes.  You can measure to your hearts delight the effects of splitting your money between different specific companies, or different industries, or different market capitalizations, or different countries or different fund managers or different whatever-metrics and doing any of those things will reduce your exposure to those specific allocations.   It may be worth pointing out that currently the hot recommendation is a plain vanilla market tracking S&P 500 index fund (that just buys some of each of the 500 largest US companies without any consideration given to risk correlation) over standard deviation calculating actively managed funds.  If you ask me that speaks volumes of the true efficacy of hyper analyzing the purported correlations of various securities.

negative: "The question is: how do you quantify investment risk? As Michael S says, one approach is to treat investment returns as a random variable. Bill Goetzmann (Yale finance professor) told me that if you accept that markets are efficient or that the price of an asset reflects it's underlying value, then changes in price represent changes in value, so standard deviation naturally becomes the appropriate measure for riskiness of an asset. Essentially, the more volatile an asset, the riskier it is. There is another school of thought that comes from Ben Graham and Warren Buffett, which says that volatility is not inherently risky. Rather, risk should be defined as the permanent loss of capital, so the riskiness of an asset is the probability of a permanent loss of capital invested.  This is easy to do in casino games, based on basic probability such as   roulette or slots. But what has been done with the various kinds of   investment risks? My point is saying that certain bonds are ""low risk""   isn't good enough; I'd like some numbers--or at least a range of   numbers--and therefore one could calculate expected payoff (in the   statistics sense). Or can it not be done--and if not, why not? Investing is more art than science. In theory, a Triple-A bond rating means the asset is riskless or nearly riskless, but we saw that this was obviously wrong since several of the AAA mortgage backed securities (MBS) went under prior to the recent US recession. More recently, the current threat of default suggests that bond ratings are not entirely accurate, since US Treasuries are considered riskless assets.  Investors often use bond ratings to evaluate investments - a bond is considered investment grade if it's BBB- or higher. To adequately price bonds and evaluate risk, there are too many factors to simply refer to a chart because things like the issuer, credit quality, liquidity risk, systematic risk, and unsystematic risk all play a factor.  Another factor you have to consider is the overall portfolio. Markowitz showed that adding a riskier asset can actually lower the overall risk of a portfolio because of diversification. This is all under the assumption that risk = variance, which I think is bunk.  I'm aware that Wall Street is nothing like roulette, but then again   there must be some math and heavy economics behind calculating risk   for individual investors. This is, after all, what ""quants"" are paid   to do, in part. Is it all voodoo? I suspect some of it is, but not all   of it. Quants are often involved in high frequency trading as well, but that's another note. There are complicated risk management products, such as the Aladdin system by BlackRock, which incorporate modern portfolio theory (Markowitz, Fama, Sharpe, Samuelson, etc) and financial formulas to manage risk.  Crouhy's Risk Management covers some of the concepts applied.  I also tend to think that when people point to the last x number of   years of stock market performance, that is of less value than they   expect. Even going back to 1900 provides ""only"" 110 years of data, and   in my view, complex systems need more data than those 40,500 data   points. 10,000 years' worth of data, ok, but not 110. Any books or articles that address these issues, or your own informed   views, would be helfpul. I fully agree with you here. A lot of work is done in the Santa Fe Institute to study ""complex adaptive systems,"" and we don't have any big, clear theory as of yet. Conventional risk management is based on the ideas of modern portfolio theory, but a lot of that is seen to be wrong. Behavioral finance is introducing new ideas on how investors behave and why the old models are wrong, which is why I cannot suggest you study risk management and risk models because I and many skilled investors consider them to be largely wrong. There are many good books on investing, the best of which is Benjamin Graham's The Intelligent Investor. Although not a book on risk solely, it provides a different viewpoint on how to invest and covers how to protect investments via a ""Margin of Safety."" Lastly, I'd recommend Against the Gods by Peter Bernstein, which covers the history of risk and risk analysis. It's not solely a finance book but rather a fascinating historical view of risk, and it helps but many things in context. Hope it helps!"

negative: it's kind of like a circular loop:  i think he would suggest identifying strategies/portfolio managers who have demonstrated outperformance in a persistent manner.  Thing is, that's also really hard to do.  I think empirically, MPT suffers when the market does. By diversifying, you'll only be down less. He's suggesting shooting for absolute returns -- no matter what the market does, he wants to see positive gains.  (a lot) easier said than done

negative: Adding international bonds to an individual investor's portfolio is a controversial subject.  On top of the standard risks of bonds you are adding country specific risk, currency risk and diversifying your individual company risk.  In theory many of these risks should be rewarded but the data are noisy at best and adding risk like developed currency risk may not be rewarded at all. Also, most of the risk and diversification mentioned above are already added by international stocks.  Depending on your home country adding international or emerging market stock etfs only add a few extra bps of fees while international bond etfs can add 30-100bps of fees over their domestic versions.  This is a fairly high bar for adding this type of diversification.  US bonds for foreign investors are a possible exception to the high fees though the government's bonds yield little. If your home currency (or currency union) does not have a deep bond market and/or bonds make up most of your portfolio it is probably worth diversifying a chunk of your bond exposure internationally.  Otherwise, you can get most of the diversification much more cheaply by just using international stocks.

negative: I don't think they could have done anything besides what they did.  There's plenty of cheaper alternatives that no one talks about because they're not as good.  Lego has been the world leader for decades because of its commitment to perfection.  I'm guessing their boom had a lot to do with their diversification.  They went pretty strong into TV shows, movies, video games...all of which are getting old.

negative: Diversification is a risk-mitigation strategy. When you invest in equities, you generally get a higher rate of return than a fixed income investment. But you have risks... a single company's market value can decline for all sorts of reasons, including factors outside of the control of management. Diversification lets you spread risk and concentrate on sectors that you feel offer the best value. Investing outside of your currency zone allows you to diversify more, but also introduces currency risks, which require a whole other level of understanding. Today, investing in emerging markets is very popular for US investors because these economies are booming and US monetary policy has been weakening the dollar for some time. A major bank failure in China or a flip to a strong dollar policy could literally implode those investments overnight. At the end of the day, invest in what you understand. Know the factors that can lower your investment value.

negative: "Years ago I wrote an article Risk, Reward, Coin Flipping which explains from a 'game theory' perspective how diversifying works to minimize standard deviation in one's returns.  It's long and tedious, not easy to summarize, but it holds up well, I'm pleased with how the analogy does its job.  Update - the above is too ""link-only"", written over 5 years ago. The article I wrote offers a mathematical approach via an understandable example of coin flipping. With just 2 options, a 'head' is a 10% loss, while a 'tail' is a 30% gain. This actually represents the market fairly well as it results in a 10% average gain and 28% standard deviation for just 2 flips. The article shows how by 'diversifying', choosing to make multiple smaller bets, the average 10% stays the same, but the standard deviation is brought down dramatically, 7.6% when we use a sample experiment with 7 coins."

negative: The software you provided as an example won't teach you much about investing. The most important things of investing are: These are the only free lunches in investing. Allocation tells you how much expected return (and also how much risk) your portfolio has. Diversification is the only way to reduce risk without reducing return; however, just note that there is market risk that cannot be eliminated with diversification. Every penny you save on costs and taxes is important, as it's guaranteed return. If you were to develop e.g. software that calculates the expected return of a portfolio when given allocation as an input, it could teach you something about investing. Similarly, software that calculates the average costs of your mutual fund portfolio would teach you something about investing. But sadly, these kinds of software are uncommon.

negative: Ditto Bill and I upvoted his answer. But let me add a bit. If everyone knew exactly what the risk was for every investment, then prices would be bid up or down until every stock (or bond or derivative or whatever) was valued at exactly risk times potential profit. (Or more precisely, integral of risk times potential profit.) If company A was 100% guaranteed to make $1 million profit this year, while company B had 50% change to make a $2 million profit and 50% to make $0, and every investor in the world knew that, then I'd expect the total price of all shares of the two stocks to stabilize at the same value. The catch to that, though, is that no one really knows the risk. The risk isn't like, we're going to roll a die and if it comes up even the company makes $1 million and if it comes up odd the company makes $0, so we could calculate the exact probability. The risk comes from lack of information. Will consumers want to buy this new product? How many? What are they willing to pay? How capable is the new CEO? Etc. It's very hard to calculate probabilities on these things. How can you precisely calculate the probability that unforeseen events will occur? So in real life prices are muddled. The risk/reward ratio should be roughly sort of approximately linear, but that's about the most one can say.

negative: "Wow, this analysis really surprised me. Very complete and useful, but i think my teacher request was easier. He just said: ""Try to build a diversified portfolio. Then try to add a commodity (like silver or gold) and understand how the risk vary introducing an asset like this."" So, i'm basically making a stocks portfolio and i'm calculating its expected return and risk. (for example 40%FB, 10%JNJ, 20%GS, 10%F and 20%MCD) then i'm adding GLD (so now i have something like 20%FB, 10%JNJ, 10%GS, 10%F and 20%MCD 30%GLD) and i'm actually making an excel spreadsheet where i calculate all the: -Expected returns -St Deviation -Covariance  At the end i compare the returns and the risks on the 2 different portfolios."

negative: "JoeTaxpayer's answer is dead on... but let me give my own two cents with a little bit of math. Otherwise, I personally find that people talking about diversified portfolios tends to be full of buzzwords.  Let's say that Buffett's investments are $10 million. He would like to earn ≥7% this year, or $700,000.  He can invest that money in coca-cola//underwear, which might return: Or he can invest in ""genius moves"" that will make headlines: (like buying huge stakes in Goldman Sachs), which might return: And he makes plays for the long haul based on the expected value of the investments. So if he splits it 50/50... ($5 million/ $5 million), then his expected value is 822,250: By diversifying, he does reduce the expected value of the portfolio... (He is not giving $10 M the chance to turn into $1.5 million or $2 million for him!). The expected value of that shock-and-awe portfolio with all $10 million invested in it is $1.2M. By taking less risk... for less reward... his expected return is lower. But his risk is lower too.  Scale this example back up into the $100 million or billion range that Buffett invests in and that extra margin makes the difference.  In the context of your original article, the lower-risk 'cake and underwear' investments let Buffett go big on the things that will make 20%+ returns on billions of dollars, without completely destroying his investment capital when things take a turn for the worse."

negative: This is just an addition to base64's answer.  In order to maximize your overall wealth (and wellbeing) in a long run, it is not enough to look only at the expected value (EV). In his example of always keeping $9850 or having $10000 99% of the time, EV in the second case is greater ($9900 > $9850) and if you are Bill Gates than you should not take an insurance in this case. But if your wealth is a lot less than that you should take an insurance. Take a look at Kelly criterion and utility functions. If I offer you to take 100 million dollars (no strings attached) or to take a risk to get 200 million dollars 60% of the time (and $0 40% of the time), would you take that risk? You shouldn't but Bill Gates should take that risk because that would be a very good investment for him. Utility functions can help you choose if you want an insurance or not. Maybe you want to insure your house because the value of the house is a large percentage of your wealth but on the other hand you don't need to insure your car if it is very easy for you to afford another one (but not easy to afford another house). Lets calculate what your wealth should be in order not to take this $150 insurance on a $10000 item. If you pay $150 for an insurance you have guaranteed $9850. But choosing not to take an insurance is the same as betting $9850 in order to gain $150 99% of the time. By using Kelly criterion formula fraction of the wealth needed to make this bet is: [p*(b+1)-1]/b = [0.99*(150/9850+1) -1]/ (150/9850) = 1/3.  That means that if your wealth greater than $29950 you don't need an insurance. But if you want to be sure it is advised to use fractional Kelly betting (for example you could multiply fraction by 1/2) and in that case if your wealth is more than $59900 you don't need an insurance for this item.

negative: Chaos theory is two essays combined as a book. It's short.  You could probably read the whole thing in under 2 hours.  Also [here is a print version](http://www.daviddfriedman.com/Libertarian/Machinery_of_Freedom/MofF_Chapter_29.html) of David Friedman's theory.  I do have a longer, more detailed explanation, but it's in video form (about an hour).

negative: Diversified is relative. Alfred has all his money in Apple.  He's done very well over the last 10 years, but I think most investors would say that he's taking an incredible risk by putting everything on one stock. Betty has stock in Apple, Microsoft, and Google.  Compared to Alfred, she is diversified. Charlie looks at Betty and realizes that she is only investing in one particular industry.  All the companies in an individual industry can have a downturn together, so he invests everything in an S&P 500 index fund. David looks at Charlie and notes that he's got everything in large, high-capitalization companies.  Small-cap stocks are often where the growth happens, so he invests in a total stock market fund. Evelyn realizes that David has all his money tied up in one country, the United States.  What about the rest of the world?  She invests in a global fund. Frank really likes Evelyn's broad approach to equities, but he knows that some portion of fixed-income assets (e.g. cash deposits, bonds) can reduce portfolio volatility—and may even enhance returns through periodic rebalancing. He does what Evelyn does, but also allocates some percentage of his portfolio to fixed income, and intends to maintain his target allocations. Being diversified enough depends on your individual goals and investing philosophy.  There are some who would say that it is wrong to put all of your money in one fund, no matter what it is.  Others would say that a sufficiently broad index fund is inherently diversified as-is.

negative: "This is the best tl;dr I could make, [original](https://www.vox.com/policy-and-politics/2017/7/7/15933674/video-games-job-supply) reduced by 93%. (I'm a bot) ***** > New research shows that the lure of computers - and video games in particular - has played a role in keeping young men from working.  > What the group of researchers discovered was fascinating: The value of young men&#039;s leisure time was increasing, and the allure of video games played a small but significant role in why they were working less.  > Hurst&#039;s research suggests that jobs need to pay a lot more to make work seem more appealing to young men - which would, in theory, make work seem more worthwhile than playing video games.   ***** [**Extended Summary**](http://np.reddit.com/r/autotldr/comments/6m3fs9/the_unexpected_economic_consequences_of_video/) | [FAQ](http://np.reddit.com/r/autotldr/comments/31b9fm/faq_autotldr_bot/ ""Version 1.65, ~162548 tl;drs so far."") | [Feedback](http://np.reddit.com/message/compose?to=%23autotldr ""PM's and comments are monitored, constructive feedback is welcome."") | *Top* *keywords*: **work**^#1 **men**^#2 **Job**^#3 **more**^#4 **young**^#5"

negative: "1. Interest rates What you should know is that the longer the ""term"" of a bond fund, the more it will be affected by interest rates. So a short-term bond fund will not be subject to large gains or losses due to rate changes, an intermediate-term bond fund will be subject to moderate gains or losses, and a long-term bond fund will be subject to the largest gains or losses. When a book or financial planner says to buy ""bonds"" with no other qualification, they almost always mean investment-grade intermediate-term bond funds (or for individual bonds, the equivalent would be a bond ladder averaging an intermediate term). If you want technical details, look at the ""average duration"" or ""average maturity"" of the bond fund; as a rough guide, if the duration is 10, then a 1% change in interest rates would be a 10% gain or loss on the fund. Another thing you can do is look at long-term (10 years or ideally longer) performance history on some short, intermediate, and long term bond index funds, and you can see how the long term funds bounced around more. Non-investment-grade bonds (aka junk bonds or high yield bonds) are more affected by factors other than interest rates, including some of the same factors (economic booms or recessions) that affect stocks. As a result, they aren't as good for diversifying a portfolio that otherwise consists of stocks. (Having stocks, investment grade bonds, and also a little bit in high-yield bonds can add diversification, though. Just don't replace your bond allocation with high-yield bonds.) A variety of ""complicated"" bonds exist (convertible bonds are an example) and these are tough to analyze. There are also ""floating rate"" bonds (bank loan funds), these have minimal interest rate sensitivity because the rate goes up to offset rate rises. These funds still have credit risks, in the credit crisis some of them lost a lot of money. 2. Diversification The purpose of diversification is risk control. Your non-bond funds will outperform in many years, but in other years (say the -37% S&P 500 drop in 2008) they may not. You will not know in advance which year you'll get. You get risk control in at least a few ways. There's also an academic Modern Portfolio Theory explanation for why you should diversify among risky assets (aka stocks), something like: for a given desired risk/return ratio, it's better to leverage up a diverse portfolio than to use a non-diverse portfolio, because risk that can be eliminated through diversification is not compensated by increased returns. The theory also goes that you should choose your diversification between risk assets and the risk-free asset according to your risk tolerance (i.e. select the highest return with tolerable risk). See http://en.wikipedia.org/wiki/Modern_portfolio_theory for excruciating detail. The translation of the MPT stuff to practical steps is typically, put as much in stock index funds as you can tolerate over your time horizon, and put the rest in (intermediate-term investment-grade) bond index funds. That's probably what your planner is asking you to do. My personal view, which is not the standard view, is that you should take as much risk as you need to take, not as much as you think you can tolerate: http://blog.ometer.com/2010/11/10/take-risks-in-life-for-savings-choose-a-balanced-fund/ But almost everyone else will say to do the 80/20 if you have decades to retirement and feel you can tolerate the risk, so my view that 60/40 is the max desirable allocation to stocks is not mainstream. Your planner's 80/20 advice is the standard advice. Before doing 100% stocks I'd give you at least a couple cautions: See also:"

negative: Index funds are well-known to give the best long-term investment. Are they? Maybe not all the time! If you had invested in an index fund tracking the S&P500 at the start of 2000 you would still be behind in terms of capital appreciation when taking inflation into considerations. Your only returns in 13.5 years would have been any dividends you may have received. See the monthly chart of the S&P500 below.  Diversification can be good for your overall returns, but diversification simply for diversification sake is as you said, a way of reducing your overall returns in order of smoothing out your equity curve. After looking up indexes for various countries the only one that had made decent returns over a 13.5 year period was the Indian BSE 30 index, almost 400% over 13.5 years, although it also has gone nowhere since the end of 2007 (5.5 years). See monthly chart below.  So investing internationally (especially in developing countries when developed nations are stagnating) can improve your returns, but I would learn about the various international markets first before plunging straight in. Regarding investing in an Index fund vs direct investment in a select group of shares, I did a search on the US markets with the following criteria on the 3rd January 2000:  If the resulting top 10 from the search were bought on 3rd January 2000 and held up until the close of the market on the 19th June 2013, the results would be as per the table below:  The result, almost 250% return in 13.5 years compared to almost no return if you had invested into the whole S&P 500 Index. Note, this table lists only the top ten from the search without screening through the charts, and no risk management was applied (if risk management was applied the 4 losses of 40%+ would have been limited to a maximum of 20%, but possibly much smaller losses or even for gains, as they might have gone into positive territory before coming back down - as I have not looked at any of the charts I cannot confirm this). This is one simple example how selecting good shares can result in much better returns than investing into a whole Index, as you are not pulled down by the bad stocks.

negative: "Typically investing in only two securities is not a good idea when trying to spread risk. Even though you are in the VTI which is spread out over a large amount of securites it should in theory reduce portfolio beta to zero, or in this case as close to it as possible. The VTI however has a beta of 1.03 as of close today in New York. This means that the VTI moves roughly in exact tandem as ""the market"" usually benched against the S&P 500, so this means that the VTI is slightly more volatile than that index. In theory beta can be 0, this would be akin to investing in T-bills which are 'assumed' to be the risk free rate. So in theory it is possible to reduce the risk in your portfolio and apply a more capital protective model. I hope this helps you a bit."

negative: "Certain parts of the black-scholes model [d2 and N(d2)] are sometimes used to predict default (Merton model).   Furthermore, using options on the firms equity, one can derive the implied volatility of them firm. This can also be reflected in the above (Merton model) to calculate the ""risk"" or volatility of the firm's assets.   Honestly there are numerous ways one can use the B/S model to price a variety of things. Did they say anymore more specific?"

negative: "What he said was:  >Short term returns show ""fat tails"" in their distribution.  This means that in the short run, rare events in the stock market, like huge up and downswings, happen much more often than you would expect given the circumstances.  >Long term returns converge towards a gaussian distribution.   This means that long term changes in stock prices show about the level of swings you would expect to see.  >The authors think there's a connection between this and the ""long memory"" of >volatility (i.e. that the autocorrelation of absolute volatilities also has a fat tail).  Auto-correlation is the idea that an event is closely related, or depends upon, a previous event.  It shouldn't be a surprise that prices can depend on previous prices.  (Contrast this with a coin toss.  Each time you toss the coin, the result is independent of any previous result.)  Normally, you would use an estimate of auto-correlation to test the randomness of your time series.  Unless you have good reason to do otherwise, you use the standard normal (or Gaussian) distribution to do so.  Some previous study, or perhaps this one, may have found that the distribution of their auto-correlation estimates for volatility (change in prices)  is not normally distributed, but rather that extreme values happen more often than would be expected (fat tail).  These guys find a correlation between the short term return fat tails, the normally  distributed long term returns, and a previous finding that the auto-correlation of volatility may have fat tails, and they think that these things could be more than simply coincidence."

negative: Hedging - You have an investment and are worried that the price might drop in the near future. You don't want to sell as this will realise a capital gain for which you may have to pay capital gains tax. So instead you make an investment in another instrument (sometimes called insurance) to offset falls in your investment.  An example may be that you own shares in XYZ. You feel the price has risen sharply over the last month and is due for a steep fall. So you buy some put option over XYZ. You pay a small premium and if the price of XYZ falls you will lose money on the shares but will make money on the put option, thus limiting your losses. If the price continues to go up you will only lose the premium you paid for the option (very similar to an insurance policy). Diversification - This is when you may have say $100,000 to invest and spread your investments over a portfolio of shares, some units in a property fund and some bonds. So you are spreading your risks and returns over a range of products. The idea is if one stock or one sector goes down, you will not lose a large portion of your investment, as it is unlikely that all the different sectors will all go down at the same time.


query: Why are historical prices of stocks different on different websites? Which one should I believe?

positive: On Monday, the 27th of June 2011, the XIV ETF underwent a 10:1 share split. The Yahoo Finance data correctly shows the historic price data adjusted for this split.  The Google Finance data does not make the adjustment to the historical data, so it looks like the prices on Google Finance prior to 27 June 2011 are being quoted at 10 times what they should be.   Coincidentally, the underlying VIX index saw a sudden surge on the Friday (24 June) and continued on the Monday (27 June), the date that the split took effect.  This would have magnified the bearish moves seen in the historic price data on the XIV ETF. Here is a link to an article detailing the confusion this particular share split caused amongst investors.  It appears that Google Finance was not the only one to bugger it up.  Some brokers failed to adjust their data causing a lots of confusion amongst clients with XIV holdings at the time. This is a recurring problem on Google Finance, where the historic price data often (though not always) fails to account for share splits.

negative: The general rule with stock options is that it's best to wait until expiration to exercise them.  The rationale depends on a few factors and there are exceptions. Reasons to wait: There would be cases to exercise early: Tax implications should be checked with a professional advisor specific to your situation. In the employee stock option plans that I have personally seen, you get regular income tax assessed between exercise price and current price at the time you exercise.  Your tax basis is then set to the current price.  You also pay capital gains tax when you eventually sell, which will be long or short term based on the time that you held the stock. (The time that you held the options does not count.)  I believe that other plans may be set up differently.

negative: "The response to this question will be different depending which of the investment philosophies you are using.  Value investors look at the situation the company is in and try to determine what the company is worth and what it will be worth in the future. Then they look at the current stock price and decide whether or not the stock is priced at a good deal or not. If the stock price is priced lower than they believe the company is worth, they would want to buy stock, and if the price rises above what they believe to be the true value, they would sell. These types of investors are not looking at the history or trend of what the price has done in the past, only what the current price is and where they believe the price should be in the future.  Technical analysis investors do something different. It is their belief that as stock prices go up and down, they generally follow patterns. By looking at a chart of what a stock price has been in the past, they try to predict where it is headed, and buy or sell based on that prediction.  In general, value investors are longer-term investors, and technical analysis investors are short-term investors.  The advice you are considering makes a lot of sense if you are using technical analysis. If you have a stock that is trending down, your strategy probably tells you to sell; buying more in the hopes of turning things around would be seen as a mistake. It is like the gambler in Vegas who keeps playing a game he is losing, hoping that his luck changes.  However, for the value investor, the historical price of a stock, and even the amount you currently have gained or lost in the stock, are essentially ignored. All that matters is whether or not the stock price is above or below the true value determined by the investor. For him, if the stock price falls and he believes the company still has a high value, it could be a signal to buy more. The above advice doesn't really apply for them.  Many investors don't follow either of these strategies. They believe that it is too difficult and risky to try to predict the future price of an individual stock. Instead, they invest in many companies all at once using index mutual funds, believing that the stock market as a whole always heads up over a long time frame. Those investors don't care at all if the prices of stock are going up or down. They simply keep investing each month, and hold until they have another use for the money. The above advice isn't useful for them at all.  No matter which kind of investing you are doing, the most important thing is to pick a strategy you believe in and follow the plan without emotion. Emotions can cause investors to make mistakes and start buying when their strategy tells them to sell.  Instead of trying to follow fortune cookie advice like ""Don't throw good money after bad,"" choose an investment strategy, make a plan, test it, and follow it, cautiously (after all, it may be a bad plan). For what it is worth, I am the third type of investor listed above. I don't buy individual stocks, and I don't look at the stock prices when investing more each month. Your description of your own strategy as ""buy and hold"" suggests you might prefer the same approach."

negative: There are many different reasons to buy property and it's important to make a distinction between commercial and residential property. Historically owning property has been part of the American dream, for multiple reasons.  But to answer your questions, value is not based on the age of the building (however it can be in a historic district). In addition the price of something and it's value may or may not be directly related for each individual buyer/owner (because that becomes subjective). Some buildings can lose there value as time passes, but the depends on multiple factors (area, condition of the building, overall economy, etc.) so it's not that easy to give a specific answer to a general question.  Before you buy property amongst many things it's important to determine why you want to buy this property (what will be it's principal use for you). That will help you determine if you should buy an old or new property, but that pales in comparison to if the property will maintain and gain in value. Also if your looking for an investment look into REIT (Real Estate Investment Trust). These can be great. Why? Because you don't actually have to carry the mortgage. Which makes that ideal for people who want to own property but not have to deal with the everyday ins-and-outs of the responsibility of ownership....like rising cost. It's important to note that the cost of purchase and cost of ownership are two different things but invariably linked when buying anything in the material strata of our world. You can find publicly traded REITs on the major stock exchanges. Hope that helps.

negative: That question makes assumptions that don't hold in general As to why to deal with futures:  Well, there's just one contract per maturity date, not a whole chain of contracts (options come at different strike prices).  That in turn means that all the liquidity is in that one contract and not scattered across the chain. Then, moreover, it depends what underlying contracts you're talking about.  Often, especially when dealing with commodities, there is no option chain on the spot product but only options on the futures contracts. In summary, the question is somewhat bogus.  Options and futures evolved historically and independently, and were not meant to be substitutable by one another.  So their rights and obligations are just a historical by-product and not their defining feature.  I suggest you refine it to a specific asset class.

negative: The net return reported to you (as a percentage) by a mutual fund is the gross return minus the expense ratio.  So, if the gross return is X% and the expense ratio is Y%, your account will show a return of (X-Y)%.  Be aware that X could be negative too. So, with Y = 1, If X = 10 (as you might get from a stock fund if you believe historical averages will continue), then the net return is 9% and you have lost (Y/X) times 100% = 10% of the gross return. If X = 8 (as you might get from a bond fund if you believe historical averages will continue), then the net return is 7% and you have lost (Y/X) times 100% = 12.5% of the gross return. and so on and so forth.  The numbers used are merely examples of the returns that have been obtained historically, though it is worth emphasizing that 10% is an average return, averaged over many decades, from investments in stocks, and to believe that one will get a 10% return year after year is to mislead oneself very badly. I think the point of the illustrations is that expense ratios are important, and should matter a lot to you, but that their impact is proportionately somewhat less if the gross return  is high, but very significant if the gross return is low, as  in money-market funds.  In fact, some money market funds which  found that X < Y have even foregone charging the expense ratio  fee so as to maintain a fixed $1 per share price.  Personally,  I would need a lot of persuading to invest in even a stock fund with 1% expense ratio.

negative: "First: do you understand why it dropped? Was it overvalued before, or is this an overreaction to some piece of news about them, or about their industry, or...? Arguably, if you can't answer that, you aren't paying enough attention to have been betting on that individual stock. Assuming you do understand why this price swing occurred -- or if you're convinced you know better than the folks who sold at that price -- do you believe the stock will recover a significant part of its value any time soon, or at least show a nice rate of growth from where it is now? If so, you might want to hold onto it, risking further losses against the chance of recovering part or all of what is -- at this moment -- only a loss on paper. Basically: if, having just seen it drop, you'd still consider buying it at the new price you should ""buy it from yourself"" and go on from here. That way at least you aren't doing exactly what you hope to avoid, buying high and selling low. Heck, if you really believe in the stock, you could see this as a buying opportunity... On the other hand, if you do not believe you would buy it now at its new price, and if you see an alternative which will grow more rapidly, you should take your losses and move your money to that other stock. Or split the difference if you aren't sure which is better but can figure out approximately how unsure you are. The question is how you move on from here, more than how you got here. What happened happened. What do you think will happen next, and how much are you willing to bet on it? On the gripping hand: This is part of how the market operates. Risk and potential reward tend to be pretty closely tied to each other. You can reduce risk by diversifying across multiple investments so no one company/sector/market can hurt you too badly --- and almost anyone sane will tell you that you should diversify -- but that means giving up some of the chance for big winnings too. You probably want to be cautious with most of your money and go for the longer odds only with a small portion that you can afford to lose on. If this is really stressing you out, you may not want to play with individual stocks. Mutual funds have some volatility too, but they're inherently diversified to a greater or lesser extent. They will rarely delight you, but they won't usually slap you this way either."

negative: It's to legally allow you to buy/ sell securities on behalf of others and to give advice. Different tests allow different things. 66 is for the basics: stocks and bonds etc. I believe 31 is for insurance or something. I'm not too sure the specifics I'm probably wrong about which test is which though.

negative: In short (pun intended), the shareholder lending the shares does not believe that the shares will fall, even though the potential investor does. The shareholder believes that the shares will rise. Because the two individuals believe that a different outcome will occur, they are able to make a trade. By using the available data in the market, they have arrived at a particular conclusion of the fair price for the trade, but each individual wants to be on the other side of it. Consider a simpler form of your question: Why would a shareholder agree to sell his/her shares? Why don't they just wait to sell, when the price is higher? After all, that is why the buyer wants to purchase the shares. On review, I realize I've only stated here why the original shareholder wouldn't simply sell and rebuy the share themselves (because they have a different view of the market). As to why they would actually allow the trade to occur - Zak (and other answers) point out that the shares being lent are compensated for by an initial fee on the transaction + the chance for interest during the period that the shares are owed for.

negative: I assume I can/will need to file an 83(b) election, in order to avoid   tax repercussions? What exactly will this save me from? 83(b) election is for restricted stock grants, not for stock purchases. For restricted stocks, you generally pay income tax when they vest. For startups the price difference between the time of the grant and the time of the vesting can be astronomical and by choosing 83(b) you effectively pay income tax on the value of the grant instead of the value of the vest. Then, you only pay capital gains tax on the difference between the sale price and the grant value when you sell. In your case you're exercising an option, i.e.: you're buying a stock, so 83(b) is irrelevant. What you will pay though is the tax on the difference between the strike price and the stock FMV (unless the stocks you end up buying are restricted - which would have been the case if you exercised your options early, but I don't think is going to be the case now). What steps should I take to (in the eyes of the law) guarantee that   the board has received my execution notice? The secretary of the board   is a notorious procrastinator and can be very unorganized. You should read what the grant contract/company policy says on that. Ask the HR/manager. Usually, a certified letter with return receipt should be enough, but you should verify the format, the address, and the timeframe.

negative: yes, i am incorporating monte carlo return scenarios for both equity and real estate.  yeah there is a lot to consider in the case of the property being a condo where you have to account for property taxes as well as condo fees.   the two projects have entirely different considerations and it's not like the money that is injected to one is similar to the other (very different) which is why i figured there should be differing discount rates.  in any case, thanks for the discussion and suggestions.

negative: "As I understand it, Implied Volatility represents the expected gyrations of an options contract over it's lifetime.  No, it represents that expected movement of the underlying stock, not the option itself.  Yes, the value of the option will move roughly in the same direction the value of the stock, but that's not what IV is measuring. I even tried staring at the math behind the Options pricing model to see if that could make more sense for me but that didn't help. That formula is correct for the Black-Scholes model - and it is not possible (or at least no one has done it yet) to solve for s to create a closed-form equation for implied volatility.  What most systems do to calculate implied volatility is plug in different values of s (standard deviation) until a value for the option is found that matches the quoted market value ($12.00 in this example).  That's why it's called ""implied"" volatility - the value is implied from market prices, not calculated directly. The thing that sticks out to me is that the ""last"" quoted price of $12 is outside of the bid-ask spread of $9.20 to $10.40, which tells me that the underlying stock has dropped significantly since the last actual trade.   If the Implied Vol is calculated based on the last executed trade, then whatever algorithm they used to solve for a volatility that match that price couldn't find a solution, which then choose to show as a 0% volatility.   In reality, the volatility is somewhere between the two neighbors of 56% and 97%, but with such a short time until expiry, there should be very little chance of the stock dropping below $27.50, and the value of the option should be somewhere around its intrinsic value (strike - stock price) of $9.18."

negative: "I'll concede that you're probably speaking in good faith- I genuinely believe that you're original statement was one that meant to point out that the ruling class seek to squeeze all the value they can out of being the ruling class, which includes maximizing the size of the rest of the population to drive down wages and get the most labor out of payrolls as possible to maximize profit. I can concede that completely and never suspected that you felt otherwise.  That said, ""reasonable"" people are often unequipped to deal with extreme or academic scenarios using reason alone. My entire point of digression came from the use of the term ""commodity,"" as it refers to things of value who's value arises from their ability to be traded at a profit. Your statement regarding people fitting this definition was true in the time of feudalism- pushing that definition back to the idea that the labor of people was tradable (but people owned themselves) was a major improvement in human rights (happening for different people at different points in history). I drew a point of contention because it's an *important* and *historical* point of contention that should never slip backwards ever, without being pointed out."

negative: "First a quick terminology correction: I believe you're proposing selling 10,000 shares of the stock of a company, not ""10,000 stocks"". When you sell, you need to decide whether you're selling for a specific minimum price or just selling for whatever price you can get. If you set a specific lower limit on asking price, then if people aren't interested at that price it doesn't sell. Which may mean you sell only a few shares, or none if your asking price isn't considered reasonable. If you want to sell independent of price, then as you begin to flood the market with your shares, the price you get per additional share may decline until it finds a buyer. What that lower limit is will depend on what people think the stock is currently worth. This is one of the many complications I don't want to deal with, which is why I stick with index funds."

negative: I haven't seen any of the other answers address this point – shares are (a form of) ownership of a company and thus they are an entitlement to the proceeds of the company, including proceeds from liquidation. Imagine an (extreme, contrived) example whereby you own shares in a company that is explicitly intended to only exist for a finite and definite period, say to serve as the producers of a one-time event. Consider a possible sequence of major events in this company's life: So why would the shares of this hypothetical company be worth anything? Because the company itself is worth something, or rather the stuff that the company owns is worth something, even (or in my example, especially) in the event of its dissolution or liquidation. Besides just the stuff that a company owns, why else would owning a portion of a company be a good idea, i.e. why would I pay for such a privilege? Buying shares of a company is a good idea if you believe (and are correct) that a company will make larger profits or capture more value (e.g. buy and control more valuable stuff) than other people believe. If your beliefs don't significantly differ from others then (ideally) the price of the companies stock should reflect all of the future value that everyone expects it to have, tho that value is discounted based on time preference, i.e. how much more valuable a given amount of money or a given thing of value is today versus some time in the future. Some notes on time preference: But apart from whether you should buy shares in a specific company, owning shares can still be valuable. Not only are shares a claim on a company's current assets (in the event of liquidation) but they are also claims on all future assets of the company. So if a company is growing then the value of shares now should reflect the (discounted) future value of the company, not just the value of its assets today. If shares in a company pays dividends then the company gives you money for owning shares. You already understand why that's worth something. It's basically equivalent to an annuity, tho dividends are much more likely to stop or change whereas the whole point of an annuity is that it's a (sometimes) fixed amount paid at fixed intervals, i.e. reliable and dependable. As CQM points out in their answer, part of the value of stock shares, to those that own them, and especially to those considering buying them, is the expectation or belief that they can sell those shares for a greater price than what they paid for them – irrespective of the 'true value' of the stock shares. But even in a world where everyone (magically) had the same knowledge always, a significant component of a stock's value is independent of its value as a source of trading profit. As Jesse Barnum points out in their answer, part of the value of stocks that don't pay dividends relative to stocks that do is due to the (potential) differences in tax liabilities incurred between dividends and long-term capital gains. This however, is not the primary source of value of a stock share.

negative: Two possible reasons: You can tell which scenario it is based on the credit history they provide you. If you look at the history and they show you your scores for each month, even though you didn't initiate it, then they are auto checking it each month. If the historical dates are only on the dates you clicked on the button, they are only checking when you manually click on it. As for the why they provide it, a few years back it was a desirable feature. Now they all do it just to keep pace with everyone else. Note that most banks only provide a single scoring model from one bureau (but different banks use different bureaus).

negative: It's a really big stretch to assume that a particular 10Q release will have the exact same impact on trading volume, trading price, and volatility as a prior release, in a different quarter, under a different set of circumstances and a different set of results, which is what you seem to be implying when you suggest that a lack of volume in response to one quarter's results should therefore be used as a benchmark.   I think traders and the HFT firms are a lot smarter than you think.

negative: Seeing a lot of comments about differing prices on the best buy website and in-store. The store has to match the price. They don't have a choice.   And I don't know if its just my store or if its company wide but we match Amazon and other websites now.

negative: The bag's style should be something traditional so it won't go out of fashion. At our company website, you can get different designs bags at affordable price. Today clutch bag is very popular. If you want to get multilateral and durable clutch bag you can pick a leather bag. These bags pick one that is a big enough space to accommodate your important things yet small enough to fit and comfort in your hands.

negative: From my experience you don't need knowledge of accounting to pick good stocks. The type of investing you are referring to is fundamental. This is finding out about the company, this websites should help you start off: http://en.tradehero.mobi/how-to-choose-a-stock-fundamental-analysis/ Investopedia will also be a useful website in techniques. A bit of knowledge in economics will be helpful in understanding how current affairs will affect a market, which will affect stock prices. However you need neither economics or accounting knowledge if you were to learn technical analysis, many doubt the workings of this technique, but in my experience it is easier to learn and practise. For example looking at charts from previous years it shows the last time there was a huge recession the dollar did well and commodities didn't. In this recession we are entering you can see the same thing happening. Read about the different techniques before limiting yourself to just looking at financial statements you may find a better technique suited to you, like these technical analysts: http://etfhq.com/blog/2013/03/02/top-technical-analysts/ Hope this helps.

negative: "No, it means that is only the notional value of that underlying asset of that contract, generally. The contract specification itself is listed on the exchange's websites, and there are really no assumptions you can make about a particular contract. Where S&P futures have one set of specifications, such as what it actually represents, how many each contract holds, how to price profits and losses... a different contract, such as FTSE 100 stock futures have a completely different set of specifications. Anyway in this one example the s&p 500 futures contract has an ""initial margin"" of $19,250, meaning that is how much it would cost you to establish that contract. Futures generally require delivery of 1,000 units of the underlying asset. So you would take the underlying asset's price and multiple it by 1,000. (what price you use is also mentioned in the contract specification), The S&P 500 index  is $1588 you mentioned, so on Jun2013 you would have to delivery $1588 x 1000, or $1,588,000. GREAT NEWS, you only have to put up 1.2% in principal to control a 1.5 million dollar asset! Although, if even that amount is too great, you can look at the E-Mini S&P futures, which require about 1/10th the capital and delivery. This answer required that a lot of different subjects be mentioned, so feel free to ask a new question about the more specific topics."

negative: "Joke warning: These days, it seems that rogue trading programs are the big market makers (this concludes the joke) Historically, exchange members were market makers. One or more members guaranteed a market in a particular stock, and would buy whatever you wanted to sell (or vice-versa). In a balanced market -- one where there were an equal number of buyers and sellers -- the spread was indeed profit for them. To make this work, market makers need an enormous amount of liquidity (ability to hold an inventory of stocks) to deal with temporary imbalances. And a day like October 29, 1929, can make that liquidity evaporate. I say ""historically,"" because I don't think that any stock market works this way today (I was discussing this very topic with a colleague last week, went to Wikipedia to look at the structure of the NYSE, and saw no mention of exchange members as market makers -- in fact, it appears that the NYSE is no longer a member-based exchange). Instead, today most (all?) trading happens on ""electronic crossing networks,"" where the spread is simply the difference between the highest bid and lowest ask. In a liquid stock, there will be hundreds if not thousands of orders clustered around the ""current"" price, usually diverging by fractions of a cent. In an illiquid stock, there may be a spread, but eventually one bid will move up or one ask will move down (or new bids will come in). You could claim that an entity with a large block of stock to move takes the role of market maker, but it doesn't have the same meaning as an exchange market maker. Since there's no entity between the bidder and asker, there's no profit in the spread, just a fee taken  by the ECN. Edit: I think you have a misconception of what the ""spread"" is. It's simply the difference between the highest bid and the lowest offer. At the instant a trade takes place, the spread is 0: the highest bid equals the lowest offer, and the bidder and seller exchange shares for money. As soon as that trade is completed, the spread re-appears. The only way that a trade happens is if buyer and seller agree on price. The traditional market maker is simply an entity that has the ability to buy or sell an effectively unlimited number of shares. However, if the market maker sets a price and there are no buyers, then no trade takes place. And if there's another entity willing to sell shares below the market maker's price, then the buyers will go to that entity unless the market's rules forbid it."

negative: While there are lots of really plausible explanations for why the market moves a certain way on a certain day, no one really knows for sure.  In order to do that, you would need to understand the 'minds' of all the market players.  These days many of these players are secret proprietary algorithms.  I'm not quibbling with the specifics of these explanations (I have no better) just pointing out that these are just really hypotheses and if the market starts following different patterns, they will be tossed into the dust bin of 'old thinking'. I think the best thing you can explain to your son is that the stock market is basically a gigantic highly complex poker game.  The daily gyrations of the market are about individuals trying to predict where the herd is going to go next and then after that and then after that etc. If you want to help him understand the market, I suggest two things.  The first is to find or create a simple market game and play it with him.  The other would be to teach him about how bonds are priced and why prices move the way they do.  I know this might sound weird and most people think bonds are esoteric but there are bonds have a much simpler pricing model based on fundamental financial logic.  It's much easier then to get your head around the moves of the bond markets because the part of the price based on beliefs is much more limited (i.e. will the company be able pay & where are rates going.)  Once you have that understanding, you can start thinking about the different ways stocks can be valued (there are many) and what the market movements mean about how people are valuing different companies. With regard to this specific situation, here's a different take on it from the 'priced in' explanation which isn't really different but might make more sense to your son: Pretend for a second that at some point these stocks did move seasonally.  In the late fall and winter when sales went up, the stock price increased in kind.  So some smart people see this happening every year and realize that if they bought these stocks in the summer, they would get them cheap and then sell them off when they go up.  More and more people are doing this and making easy money.  So many people are doing it that the stock starts to rise in the Summer now.  People now see that if they want to get in before everyone else, they need to buy earlier in the Spring.  Now the prices start rising in the Spring.  People start buying in the beginning of the year... You can see where this is going, right?  Essentially, a strategy to take advantage of well known seasonal patterns is unstable.  You can't profit off of the seasonal changes unless everyone else in the market is too stupid to see that you are simply anticipating their moves and react accordingly.

negative: "No, you cannot. ISO are given to you in your capacity as an employee (that's why it is ""qualified""), while your IRA is not an employee. You cannot transfer property to the IRA, so you cannot transfer them to the IRA once you paid for them as well. This is different from non-qualified stock options (discussed in this question), which I believe technically can be granted to IRA. But as Joe suggests in his answer there - there may be self-dealing issues and you better talk to a licensed tax adviser (EA/CPA licensed in your State) if this is something you're considering to do."

negative: As others have pointed out, the value of Apple's stock and the NASDAQ are most likely highly correlated for a number of reasons, not least among them the fact that Apple is part of the NASDAQ. However, because numerous factors affect the entire market, or at least a significant subset of it, it makes sense to develop a strategy to remove all of these factors without resorting to use of an index. Using an index to remove the effect of these factors might be a good idea, but you run the risk of potentially introducing other factors that affect the index, but not Apple. I don't know what those would be, but it's a valid theoretical concern.  In your question, you said you wanted to subtract them from each other, and only see an Apple curve moving around a horizontal line. The basic strategy I plan to use is similar but even simpler. Instead of graphing Apple's stock price, we can plot the difference between its stock price on business day t and business day t-1, which gives us this graph, which is essentially what you're looking for:  While this is only the preliminaries, it should give you a basic idea of one procedure that's used extensively to do just what you're asking. I don't know of a website that will automatically give you such a metric, but you could download the price data and use Excel, Stata, etc. to analyze this.  The reasoning behind this methodology builds heavily on time series econometrics, which for the sake of simplicity I won't go into in great detail, but I'll provide a brief explanation to satisfy the curious. In simple econometrics, most time series are approximated by a mathematical process comprised of several components: In the simplest case, the equations for a time series containing one or more of the above components are of the form that taking the first difference (the procedure I used above) will leave only the random component. However, if you want to pursue this rigorously, you would first perform a set of tests to determine if these components exist and if differencing is the best procedure to remove those that are present. Once you've reduced the series to its random component, you can use that component to examine how the process underlying the stock price has changed over the years. In my example, I highlighted Steve Jobs' death on the chart because it's one factor that may have led to the increased standard deviation/volatility of Apple's stock price. Although charts are somewhat subjective, it appears that the volatility was already increasing before his death, which could reflect other factors or the increasing expectation that he wouldn't be running the company in the near future, for whatever reason. My discussion of time series decomposition and the definitions of various components relies heavily on Walter Ender's text Applied Econometric Time Series. If you're interested, simple mathematical representations and a few relevant graphs are found on pages 1-3. Another related procedure would be to take the logarithm of the quotient of the current day's price and the previous day's price. In Apple's case, doing so yields this graph:  This reduces the overall magnitude of the values and allows you to see potential outliers more clearly. This produces a similar effect to the difference taken above because the log of a quotient is the same as the difference of the logs The significant drop depicted during the year 2000 occurred between September 28th and September 29th, where the stock price dropped from 26.36 to 12.69. Apart from the general environment of the dot-com bubble bursting, I'm not sure why this occurred. Another excellent resource for time series econometrics is James Hamilton's book, Time Series Analysis. It's considered a classic in the field of econometrics, although similar to Enders' book, it's fairly advanced for most investors.  I used Stata to generate the graphs above with data from Yahoo! Finance: There are a couple of nuances in this code related to how I defined the time series and the presence of weekends, but they don't affect the overall concept. For a robust analysis, I would make a few quick tweaks that would make the graphs less appealing without more work, but would allow for more accurate econometrics.

negative: "The tax comes when you close the position. If the option expires worthless it's as if you bought it back for $0. There's a short-term capital gain for the difference between your short-sale price and your buyback price on the option. I believe the capital gain is always short-term because short sales are treated as short-term even if you hold them open more than one year. If the option is exercised (calling away your stock) then you add the premium to your sale price on the stock and then compute the capital gain. So in this case you can end up treating the premium as a long-term capital gain. See IRS pub 550 http://www.irs.gov/publications/p550/ch04.html#en_US_2010_publink100010619 Search for ""Writers of puts and calls"""

negative: "Depends. The short answer is yes; HSBC, for instance, based in New York, is listed on both the LSE and NYSE. Toyota's listed on the TSE and NYSE. There are many ways to do this; both of the above examples are the result of a corporation owning a subsidiary in a foreign country by the same name (a holding company), which sells its own stock on the local market. The home corporation owns the majority holdings of the subsidiary, and issues its own stock on its ""home country's"" exchange. It is also possible for the same company to list shares of the same ""pool"" of stock on two different exchanges (the foreign exchange usually lists the stock in the corporation's home currency and the share prices are near-identical), or for a company to sell different portions of itself on different exchanges. However, these are much rarer; for tax liability and other cost purposes it's usually easier to keep American monies in America and Japanese monies in Japan by setting up two ""copies"" of yourself with one owning the other, and move money around between companies as necessary. Shares of one issue of one company's stock, on one exchange, are the same price regardless of where in the world you place a buy order from. However, that doesn't necessarily mean you'll pay the same actual value of currency for the stock. First off, you buy the stock in the listed currency, which means buying dollars (or Yen or Euros or GBP) with both a fluctuating exchange rate between currencies and a broker's fee (one of those cost savings that make it a good idea to charter subsidiaries; could you imagine millions a day in car sales moving from American dealers to Toyota of Japan, converted from USD to Yen, with a FOREX commission to be paid?). Second, you'll pay the stock broker a commission, and he may charge different rates for different exchanges that are cheaper or more costly for him to do business in (he might need a trader on the floor at each exchange or contract with a foreign broker for a cut of the commission)."

negative: Two big differences from the Digg days: 1) apps exist, meaning a large percentage of users will not even notice the redesign if they don't use the website. 2) Digg changed both functionality and design, but I believe reddit is only proposing to change design (so far).

negative: "TL;DR: Sure, ""do your own homework"" is sometimes a cop out. But that doesn't mean we shouldn't do our homework. I agree that in many cases this is a cop-out by commentators. However, even if you believe in perfect market efficiency, there is benefit in ""doing your homework"" for many reasons. One of which you already mention in the question: different stocks all with the same ""value"" might have widely ranging risk. Another factor that might vary between stocks is their tax consequences. High dividend stocks might be a better fit for some buyers than others. One stock might be priced at $40 because there is a small chance they might get regulatory approval for a new product. This might make this stock very risky with a 20% of being $150 in 12 months, and a 80% chance of being $20. Another stock might be priced at $40 because the company is a cash cow, declining in revenues but producing a large dividend of $0.40 per quarter. Low risk, but also with some potential tax disadvantages. Another stock might be priced at $40 because it's a high growth stock. This would be less risky than the first example, but more risky than the second example. And the risk would be more generalized, i.e. there wouldn't be one day or one event that would be make or break the stock. In short, even if we assume that the market is pricing everything perfectly, not all stocks are equal and not all stocks are equally appropriate to everyone. Sometimes when we hear an analyst say ""they should have done their homework"" they are really saying ""This was a high risk/high reward stock. They should have known that this had a potential downside."" And that all assumes that we believe in 100% pure market efficiency. Which many disagree with, at least to some extent. For example, if we instead subscribe to Peter Lynch's theories about ""local knowledge"", we might believe that everyone has some personal fields of expertise where they know more than the experts. A professional stock analyst is going to follow many stocks and many not have technical experience in the field of the company. (This is especially true of small and mid cap stocks.) If you happen to be an expert in LED lighting, it is entirely feasible (at least to me) that you could be able to do a better job of ""doing homework"" on CREE than the analysts. Or if you use a specialized piece of software from a small vendor at work, and you know that the latest version stinks, then you will likely know more than the analyst does. I think it is somewhat akin to going to a doctor. We could say to ourselves ""the doctor is more knowledgeable about me than medicine, I'm just going to do what they tell me to do."" And 99% of the time, that is the right thing to do. But if we do our ""homework"" anyway, and research the symptoms, diagnoses, and drugs ourselves as well, we can do get benefits. Sometimes we just can express our preferences amongst equal solutions. Sometimes we can ask smarter questions. And sometimes we have some piece of knowledge that the doctor doesn't have and can actually make an important discovery they didn't know. (And, just like investing, sometimes we can also have just enough knowledge to be dangerous and do ourselves harm if we go against the advice of the professionals.)"

negative: There are two independent sets of terms we need to define in order to answer your question.  I am trying to understand the difference between Value, Blend, and Growth These are different categories of mutual funds: Value: discounted or undervalued stocks. This is often measured by a difference between the stock's price and the Net Asset Value (NEV). Growth: stocks that fund managers believe are poised for significant growth (increase in stock price and NEV). Blend: a blend of two categories of stocks. In this context it probably refers to a combination of growth and value stocks, but it just depends on the context.  I want to receive dividend and Growth These are ways to receive earnings from a stock or fund. Dividend: a direct cash payment from owning a stock or a fund. Stocks and funds who pay out 100% of their profits don't have any money leftover to grow themselves and either stagnate or shrink. Growth: an increase manifesting itself in capital gains. If a stock or fund pays out zero dividends, then all profits are invested back into the company for fund, increasing its value. If you intend to automatically reinvest dividends, then receiving dividends is essentially the same as receiving profit through capital gains. If you intend to sell stocks or funds periodically to get some extra spending cash, then receiving profits through capital gains is essentially the same as dividends.

negative: This is a great question for understanding how futures work, first let's start with your assumptions The most interesting thing here is that neither of these things really matters for the price of the futures.  This may seem odd as a futures contract sounds like you are betting on the future price of the index, but remember that the current price already includes the expectations of future earnings as well! There is actually a fairly simple formula for the price of a futures contract (note the link is for forward contracts which are very similar but slightly more simple to understand).  Note, that if you are given the current price of the underlying the futures price depends essentially only on the interest rate and the dividends paid during the length of the futures contract.  In this case the dividend rate for the S&P500 is higher than the prevailing interest rate so the futures price is lower than the current price.  It is slightly more complicated than this as you can see from the formula, but that is essentially how it works. Note, this is why people use futures contracts to mimic other exposures.  As the price of the future moves (pretty much) in lockstep with the underlying and sometimes using futures to hedge exposures can be cheaper than buying etfs or using swaps. Edit: Example of the effect of dividends on futures prices For simplicity, let's imagine we are looking at a futures position on a stock that has only one dividend (D) in the near term and that this dividend happens to be scheduled for the day before the futures' delivery date.  To make it even more simple lets say the price of the stock is fairly constant around a price P and interest rates are near zero.  After the dividend, we would expect the price of the stock to be P' ~ P - D as if you buy the stock after the dividend you wouldn't get that dividend but you still expect to get the rest of the value from additional future cash flows of the company. However, if we buy the futures contract we will eventually own the stock but only after the dividend happens.  Since we don't get that dividend cash that the owners of the stock will get we certainly wouldn't want to pay as much as we would pay for the stock (P).  We should instead pay about P' the (expected) value of owning the stock after that date.   So, in the end, we expect the stock price in the future (P') to be the futures' price  today (P') and that should make us feel a lot more comfortable about what we our buying.  Neither owning the stock or future is really necessarily favorable in the end you are just buying slightly different future expected cash flows and should expect to pay slightly different prices.

negative: Compound interest is your friend. For such a low amount of cash, just pop it into savings accounts or deposits. When you reach about 1.500€ buy one very defensive stock that pays high dividends. With deposits, you don't risk anything, with one stock, you can lose 100% of the investment. That's why it's important to buy defensive stock (food, pharma, ...). Every time you hit 1.500€ after, buy another stock until you have about 10 different stock in different sectors, in different countries. Then buy more stock of the ones you have in portfolio. You're own strategy is pretty good also.

negative: "So, the soviet union purchases its own debt, and this is a shining example of a historical empire that worked in your mind? Come on man, you aren't that fucking stupid are you? You don't need me to explain why that is a very, very incorrect choice do you?  I asked you to name an empire, historically, that purchased its own debt and was successful in doing so. You have still yet to do that.  And btw, there are many, many different forms of ""fallacies"", don't be a redditor and only learn one. Ad hominem is the same thing as saying personal attacks, and its pretty overused on this site."