1. The Logic of Individual Choice: The Foundation of Supply and Demand 10 The Logic of Individual Choice: The Foundation of Supply and Demand The theory of economics must begin with a correct theory of consumption. — Stanley Jevons CHAPTER 10 Copyright © 2010 by the McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill/Irwin

2. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Chapter Goals Discuss the principle of diminishing marginal utility Explain how the principle of rational choice accounts for the laws of supply and demand Explain the relationship between marginal utility and price when a consumer is maximizing total utility Summarize the principle of rational choice Name three assumptions of the theory of choice and discuss why they may not reflect reality Give an example of how behavioral economics changes the assumption of utility maximization 10-2

3. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Utility Theory and Individual Choice According to this theory, two things determine what people do: Utility which is the pleasure people get from doing or consuming something According to traditional economists, our behavior is motivated by rational self interest The price of doing or consuming that something 10-3

4. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Total Utility and Marginal Utility Marginal utility is the satisfaction you get from the consumption of one additional unit of the product above and beyond what you have consumed up to that point Utility = Satisfaction Total utility is the total satisfaction one gets from consuming a product 10-4

5. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Application: Total Utility and Marginal Utility Number of Pizza SlicesTotal UtilityMarginal Utility 0014 1 12 226 10 336 8 444 6 550 4 654 2 756 0 8 -2 954 10-5

6. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Application: Comparative Advantage Utility Q The total utility curve is bowed downward 10 60 40 50 70 Utility Q 1 2 3 4 5 6 7 8 Total Utility CurveMarginal Utility Curve The marginal utility curve is downward sloping and graphed at the halfway point 1 2 3 4 5 6 7 8 30 20 2 12 8 10 14 6 4 –2 0 10-6

7. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Diminishing Marginal Utility As additional units are consumed, marginal utility decreases, but total utility continues to increase When total utility is at a maximum, marginal utility is zero The principle of diminishing marginal utility states that after some point, the marginal utility received from each additional unit of a good decreases with each additional unit consumed Beyond this point, total utility decreases and marginal utility is negative 10-7

8. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Rational Choice and Marginal Utility Any choice that does not give you as many units of utility as possible for the same amount of money is an irrational choice According to the basic principle of rational choice people spend their money on those goods that give them the most marginal utility per dollar Rational individuals want as much satisfaction as they can get from their available resources 10-8

9. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Rational Choice and Marginal Utility Consume another unit of X if: Consume another unit of Y if: The principle of rational choice states that people spend their money on those goods the give them the most marginal utility (MU) per dollar 10-9

10. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Maximizing Utility and Equilibrium The utility maximizing rule states that when the ratios of the marginal utility to price of the two goods are equal, you are maximizing utility If, you are maximizing utility 10-10

11. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Application: Maximizing Utility Big Macs (P = $2) QTUMUMU/P 002010 120 147 234 105 344 31.5 447 00 5 -5-2.5 642 -10-5 732 Ice Cream (P = $1) QTUMUMU/P 0029 1 17 246 77 353 22 455 11 556 00 6 -4 752 Suppose you have $7 to spend. How will you spend it? 10-11

12. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Extending the Principle of Rational Choice Utility is maximized when: The cost per additional unit of utility is equal for all goods and the consumer is as well off as is possible A person’s choice of how much to work is made simultaneously with the person’s decision of how much to consume 10-12

13. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Rational Choice and the Law of Demand Quantity demanded falls as price rises When the price of a good decreases, the MU/$ increases, and we consume more of it and its marginal utility decreases When the price of a good goes up, the marginal utility per dollar (MU/$) from it goes down, and we consume less of it and its marginal utility increases Quantity demanded increases as price falls 10-13

14. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Rational Choice and the Law of Demand The income effect is the reduction in quantity demanded when price increases because the price increase makes one poorer The substitution effect is the reduction in quantity demanded when price increases because you substitute another good for the more expensive one The inverse relationship between price and quantity demanded is due to the income and substitution effects Income and substitution effects 10-14

15. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Application: Income and Substitution Effects Big Macs (P = $2) QTUMUMU/P 002010 120 147 234 105 344 Ice Cream (P = $2) QTUMUMU/P 00 2914.5 129 178.5 246 73.5 353 Suppose ice cream is now $2 You are given an extra $3 to make up for this price increase so there is no income effect How will your spending change (substitution effect)? 10-15

16. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Rational Choice and the Law of Supply and the price of supplying something goes up, you supply more of that good and the price of supplying something goes down, you supply less of that good According to the principle of rational choice, if there is diminishing marginal utility… 10-16

17. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Application: Wage Rates and Labor Supply S Wage Hours per week The higher the wage, the higher the marginal utility of the goods you can get for the wage This gives an upward sloping supply curve $8.00 20 $10.00 $8.50 21 26 10-17

18. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Opportunity Cost In the context of utility, it is the marginal utility per dollar you forgo from consuming the next-best alternative If the MU X /P X > MU Y /P Y, the opportunity cost of not consuming good x is greater than the opportunity cost of not consuming good Y so we consume X Opportunity cost is the benefit forgone of the next- best alternative According to the principle of rational choice, to maximize utility, choose goods until the opportunity cost of all alternatives are equal 10-18

19. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Applying the Theory of Choice to the Real World Those assumptions are: The assumptions underlying the theory of rational decision making place limits on the use of the theory 1.Decision making is costless 2.Tastes are given 3.Individuals maximize utility Behavioral economists question all three assumptions 10-19

20. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Applying the Theory of Choice to the Real World Most people may use bounded rationality which is rationality based on rules of thumb The costs of deciding among hundreds of possible choices may lead us to do some things that seem irrational “You get what you pay for” is the implication that high price equals high quality “Follow the leader” leads to focal point equilibria in which a set of goods is consumed because they have become focal points to which people have gravitated Decision making is costless 10-20

21. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Applying the Theory of Choice to the Real World Tastes are often significantly influenced by society Implicit in the theory of rational choice is that utility functions are given, not shaped by society Conspicuous consumption is the consumption of goods not for one’s direct pleasure, but to show off to others Tastes are given “Given tastes” is the assumption on which an economic analysis is conducted 10-21

22. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Applying the Theory of Choice to the Real World Behavioral economics have found through experiments that many people do not maximize utility People may not behave rationally in practice The experiment of the ultimatum game shows that people care about fairness as well as income Individuals maximize utility Experiments also reveal a status quo bias where individuals’ actions are influenced by the current situation, even when that reasonably does not seem to be very important to the decision 10-22

23. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Chapter Summary Total utility is the satisfaction obtained from consuming a product Marginal utility is the satisfaction obtained from consuming one additional unit of a product The principle of diminishing marginal utility states that after some point, the marginal utility of consuming more of the good will fall 10-23

24. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Chapter Summary Utility is maximized and equilibrium reached when: Unless MU X /P X = MU Y /P Y, an individual can rearrange his or her consumption to increase total utility The laws of demand and supply can be derived from the principle of rational choice 10-24

25. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Chapter Summary If the price of a good increases, you will decrease consumption of that good so that its marginal utility increases If your wage rises, the marginal utility of the goods you can buy with your wage will rise and you will work more to maximize utility Behavioral economists argue that the assumptions of the theory of choice, costless decision making, given tastes, and utility maximization may not always apply when people make decisions 10-25

26. The Logic of Individual Choice: The Foundation of Supply and Demand 10 Preview of Chapter 11: Game Theory, Strategic Decision Making, and Behavioral Economics Explain why game theory is more flexible than traditional models of market behavior Explain what is meant by Nash equilibrium Provide an example of a prisoner’s dilemma game Distinguish between a dominant strategy and a mixed strategy Give two examples of seemingly irrational behavior that behavioral economists are attempting to explain and include in their economic models Explain why economists’ traditional models remain relevant even if the findings of behavioral economists are true for many, and even most, individuals 10-26