<prompt> Human: A lot of advice I get from this forum about passive investment is that put money in a low cost index fund and forget about it. But I dont understand how that is a good idea in a time like now when the stocks are priced so high. For example, if a person wouldve invested in a low cost index fund in 1999, wouldnt it be the case that ten years later he had very little appreciate of assets? So I guess my question is this, if I have 10000 to put away now is a low cost index fund still the best choice or do I wait for the market to come down?  <response>: Over any 20-year period in the last 100 years, the stock market has had a positive return. If your investment horizon is long-term, dont worry about short-term market performance, just jump in. If youre contributing regularly and the market turns down, you will get more bang for your buck as you buy those stocks on sale. 