Chapter 2 Introduces the Key Principles That Are Central to All Economic Theory


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The Key Principles
of Economics

Chapter Summary

Chapter 2 introduces the key principles that are central to all economic theory:

  • The principle of opportunity cost states that the opportunity cost of something is what you sacrifice to get it. Opportunity costs in production are generally increasing, and thus, the production possibilities curve is bowed outward.
  • The marginal principle states that any activity should be increased as long as the marginal benefits of the additional activity exceed the marginal costs.
  • The principle of voluntary exchange states that a voluntary exchange between two people makes both people better off.
  • The principle of diminishing returns states that, in the short run, if use of one input is increased while all others are held constant, production will eventually increase at a decreasing rate.
  • The real-nominal principle states that what matters to people is the real value or purchasing power of money or income, not its face or nominal value.

Learning Objectives:

1.Apply the principle of opportunity cost.

2.Apply the marginal principle.

3.Apply the principle of voluntary exchange.

4.Apply the principle of diminishing returns.

5.Apply the real-nominal principle.

Approaching the Material

Continue the approach you developed in the first chapter, reaching students where they are. The decision to go to college is a great illustration of opportunity costs because students forgo earnings that they would have received from a full-time job. Apply the concept of diminishing returns to hours studying: If a student studies for five hours, will studying one additional hour really benefit him or her? Most of the students will have had jobs, so use the price of a gallon of gas or a burger per hour worked to explain real wages. Most students will have trouble with the marginal principle,so have plenty of examples ready. A seat on a bus or train that is not full is a good example. An extra passenger in a car for a road trip or another person watching a movie will also work.

Chapter Outline

2.1The Principle ofOpportunity Cost


1.The opportunity cost of something is what you sacrifice to get it.

2.What you sacrifice is the next best alternative.

3.For example, if you choose to buy a cup of coffee, you are giving up the money it costs to buy it.What else would you have used the $2.00 for?The opportunity cost of the coffee is the one thing (or next best alternative) that you would buy if not the coffee.

Teaching Tip

Ask the students what they would be doing if they weren’t in class.Answers will range from sleeping, working, watching TV, studying, etc.You can make the point that the alternatives are infinite and computing the cost of them all is impossible.However, since they could only be doing one thing (not all of them) if they were not in class, determining the opportunity cost requires only knowing the one thing they would be doing.

B.The Cost of College

  1. The classic example of opportunity cost is the costs of going to college.Be sure to illustrate the implicit opportunity cost of forgone income as well as tuition, books, etc.

Teaching Tip

It’s also helpful to have a discussion about whether room and board should be considered a cost of college.If the person has to pay the same amount for room and board whether he/she goes to college or works, it should not be considered a cost of college.

C.The Cost of Military Spending

D.Opportunity Cost and the Production Possibilities Curve

1. The production possibilities curve:A curve that shows the possible combinations of products that an economy can produce, given that its productive resources are fully employed and efficiently used.

2. Discussion of relevant points on the production possibilities graph

a.Points on the curve are efficient and indicate an economy is utilizing all resources.

b.Points inside the curve are inefficient and indicate an economy is not utilizing all resources or resources are not used in the least-cost manner.

c.Points outside the curve are not feasible given current technologies and resources.

3.Shifts in the Production Possibilities Curve.Show how points outside the PPC are feasible in the future if it shifts out due to increases in resources or technological innovation.It is also useful to discuss what might make the PPC shift in: a natural disaster, the Y2K bug, etc.

a. Increased resources

b. Technological innovation

Teaching Tip

Use something students are familiar with to construct their first production possibilities curve. Pick two classes, such as Economics and Marketing. Tell them they are going to allocate study time to produce grades in the classes. The choice involves how much study time to allocate for each class. You can start with an all-or-nothing scenario producing an A|F outcome and make adjustments from there. Once they are comfortable, remind them that everything else was held constant. Ask them what would happen to the curve if the professors were better teachers, if students had better study skills, smaller classes, better textbooks, upgraded computers, or more time to study.

Review this key question and the related application:

Question 1:What is the opportunity cost of running a business?


This Application gives an example of a business to explain how we can use the principle of opportunity cost to compute a business’s costs. In a business, the total costs are affected by the costs of raw materials, the opportunity costs of funds invested, and the opportunity costs of time. This Application shows that we must include not just the costs of materials but also the opportunity cost of funds invested, as well as the opportunity costs of time in computing the true cost of running a business.

2.2The Marginal Principle


1.Marginal benefit is the additional benefit resulting from a small increase in some activity.

2.Marginal cost is the additional cost resulting from a small increase in some activity.

3.Choose a level of the activity such that marginal benefit of the last unit equals the marginal cost of the last unit.

B.Using the Marginal Principle:Movie Sequels, Renting College Facilities, Automobile Emissions Standards, Driving Speed and Safety

Teaching Tip

There are several easy-to-understand examples of the Marginal Principle in the world of college students. An easy way to start is with examples where the marginal cost is zero: The amount of food consumed at a particular meal in the cafeteria; Internet minutes in the computer lab; cell phone weekend minutes with some plans. Given that the marginal costs are zero, the student’s decision to consume is based on positive marginal benefits. You can then introduce situations where there are positive marginal costs, such as fast food that needs to be paid for.

Review this key question and the related application:

Question2:How do people think at the margin?

Application 2: HOW FAST TO SAIL?

This Application explains the factors that go into the decision regarding how fast to sail an ocean cargo ship. We can use the marginal principle to see that the increase in a ship’s speed depends on the marginal benefit of delivering more cargo compared to the cost of additional fuel. If the marginal benefit (the increase in revenue from delivered cargo) is greater than the marginal cost (the increase in fuel cost), the ship operator will increase the ship’s speed.

2.3The Principle of Voluntary Exchange

A.The assumption is that people act in their own self-interest. A voluntary exchange between two people makes both better off. Markets work because they are based on the principle of voluntary exchange.

Teaching Tip

College students easily understand the principle of voluntary exchange because they are constantly engaged in voluntary exchanges. Work and consumption are two examples from their world. If they are employed, they voluntarily exchange their time and effort for the money they earn. Nobody kidnaps them and forces them to work. Their employer pays them voluntarily as well. Both the student and employer are better off. Any time individuals purchase anything, they exchange money for a product or a service, making both the buyer and the seller better off.Ask students what they purchased yesterday or today:Coffee or soda?Candy?Newspaper? Why did they purchase it?

B.Exchange and Markets

  1. A market is an institution or arrangement that allows buyers and sellers to exchange goods and services.

Teaching Tip

Create a market in the classroom. Do the experiment described in the book or in MyEconLab.

C.Online Games and Market Exchange

  1. Online games such as EverQuest illustrate how markets and exchange develop on their own because of the desire to trade.

Review this key question and the related application:

Question 3:What is the rationale for specialization and exchange?


This Application illustrates how we can use the principle of voluntary exchange to explain why Mr. Johns, a very productive art painter, should hire the less productive house painter to paint his house. The opportunity cost of Mr. Johns painting the house himself would be the income lost by spending time painting the house rather than painting art and earning money for it. Mr. Johns could hire the house painter to paint the house for less money than he would lose by painting the house himself and not earn money by painting art during that time.

2.4The Principle of Diminishing Returns

A.Principle of Diminishing Returns: Suppose that output is produced with two or more inputs, and we increase one input while holding the others constant.Eventually, output will begin to increase at a decreasing rate.

Teaching Tip

Have the students picture the front end of a fast-food franchise, such as McDonald’s, Burger King, Wendy’s, or another franchise near you.Ask themwhat would happen if you kept on adding more and more workers at McDonald’s.All the equipment is fixed. The number of workers is the variable input. Ask students what would happen to the number of hamburgers served as you increased the number of workers from 1 to 3 to 5 to 50. Eventually the restaurant would be so crowded that none of the workers would be able to move or serve any hamburgers. (Make sure to point out that this is well beyond the point of diminishing returns.)

B. Diminishing Returns from Sharing a Production Facility

1. A good example of diminishing returns is when a company tries to add workers to an existing production facility.Eventually, the facility will become overcrowded, and the additional output resulting from additional workers will fall.

Review this key question and the related application:

Question 4:Do farmers experience diminishing returns?

Application 4:Fertilizer and Crop Yields

This Application illustrates how the notion of diminishing returns applies to all inputs to the production process. For a farmer, continuously increasing the amount of fertilizer applied to a fixed amount of land eventually reduces the increases in output. The farmer will experience diminishing return because, while even though the amount of fertilizer was not fixed, the other inputs to the production process are fixed.

Teaching Tip

A classroom full of urban or suburban students might not relate very well to this example.You can use watering the lawn instead. An excessive amount of water will not help the lawn grow faster.

2.5The Real-Nominal Principle


1.What matters to people is the real value or purchasing power of money or income, not its face value.

2.The nominal value of an amount of money is its face value.The real value is the value of an amount of money in terms of what it can buy.

B.The Design of Public Programs

C.The Value of the Minimum Wage

When the government publishes statistics about the economy, it takes into account the real-nominal principle.For example, the value of “real wages” shows what has happened to the purchasing power of workers over time.The nominal wage shows what has happened to the sum on the worker’s paycheck, but it cannot show what has happened to purchasing power.

Teaching Tip

Ask the students how many of them would be happy to earn $500,000 per year. Most will say yes. Then tell them that a case of soda pop costs $100, a CD costs $250, and a new car costs $500,000. Are they still happy? You can now proceed to explain the difference between nominal and real variables.

Review this key question and the related application:

Question 5: How does inflation affect lenders and borrowers?

Application 5:Repaying student Loans

This Application shows how inflation can impact the value of money paid back over time. Using changes in annual salaries, the Application demonstrates the work time it takes someone to pay back the loan under various inflation assumptions.

Teaching Tip

Another way to illustrate this concept is to ask students if they know their parents’ monthly mortgage payments and when they purchased their homes.Inflation in home prices affects the amount that people will have to borrow.An older home usually will have a smaller nominal mortgage payment.However, your students’ parents’ salaries have presumably risen partly due to inflation.Therefore, inflation has helped those whohave been debtors.

Additional Applications to Use in Class

Question:Has fish production reached the point of diminishing returns?

ADDITIONAL APPLICATION: So Long Seafood? Experts Warn of Disaster

MSNBC Staff and News Service Reports

“So Long Seafood? Experts Warn of Disaster”

Posted on

Financial Times

Posted 11/03/2006

Summary: Key Points in the Article

According to some experts, overfishing and pollution will virtually wipe out all the world’s fisheries by the year 2050.A team of economists and ecologists arrived at that conclusion by extrapolating current trends. The team warned that unless fisheries management practices radically change, we were in the “last century of wild seafood.”

The team spent four years using controlled experiments and existing data to arrive at their conclusions.However, industry professionals do not appear to share the concerns.The National Fisheries Institute issued a statement that said, “Fish stocks naturally fluctuate in population,” and “By developing new technologies that capture target species more efficiently and result in less impact on other species or the environment, we are helping to ensure our industry does not adversely affect surrounding ecosystems or damage native species.”

Seafood consumption is up in the United States, with the average American eating 16.6 pounds of seafood in 2004 versus 15.2 pounds in 2002.Fishing accounts for over $80 billion in revenue worldwide.

Analyzing the News

Note that the National Fisheries Institute did not deny declining fish stocks.Instead the organization indicated the decline was part of a natural cycle.Could it be that the increasing global demand for seafood has pushed fishing to the point of diminishing returns?

Thinking Critically Questions

  1. It appears that fish harvests are increasing, but overall fish stocks may be declining.What economic principle is exhibited?
  1. How can we increase production?
  2. At what point would we cease to add fishing boats?

Question: How can people invest in themselves?

Aleccia, JoNel

Posted 12/5/2008 on

Summary: Key Points in the Article

The shrinking economy has had an impact on people’s willingness to donate plasma, sperm, and fertile eggs. Hair sales are up as well. While the practice of selling most body products is illegal in the United States, there are instances where people are considered “compensated donors.” For example, many plasma centers will pay $20 for donor time and travel. The sudden spike in donor applications begs the question of whether the motives are altruistic or financial.

Donating fertile eggs can be lucrative. One nursing student reported being able to graduate from college debt free due to the $28,000 she received for fourcycles of fertile eggs donated since February. Viable sperm donors can earn $600 a month for a cycle of ten donations.

While the practice can earn some cash, only a small fraction of donors make it through the rigorous medical and life history screens for fertile eggs and sperm. In any case, applications to be donors are up 20 to 30 percent at most clinics with plasma donations up as much as 50 percent in some areas. The uptick appears to be consistent with the recession.

Analyzing the News

Since “price” appears fixed for these items you simply see an increase in overall quantity. However, this article begs the question of whether body parts and products should be available for sale instead of merely compensation for time and travel. What do you think?