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The Law of Demand

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Chapter Questions

Chapter Questions

quantity,quality,and price of the good or service being exchanged.Asymmetric information exists when some market participants have more and better information about the goods and services being exchanged.Fraud can arise in the presence of asymmetric information.In extreme cases,the knowledge that some market participants have access to privileged information may result in a complete breakdown of the market,such as might occur if it became widely believed that stock market transactions were dominated by insider trading.

Goods and services are said to be “private”when all the production costs and consumption benefits are borne exclusively by the market participants. That is,there are no indirect,third-party effects.Such third-party effects, called externalities,may affect either consumers or producers.The most common example of a negative externality in production is pollution.Finally, “market power”refers to the ability to influence the market price of a good or service by shifting the demand or supply curve.

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A violation of any of the three assumptions just given could lead to failure of the market to provide socially optimal levels of particular goods or services.When this occurs,direct or indirect government intervention in the market may be deemed to be in the public’s best interest.Market failure and government intervention will be discussed at some length in Chapter 15.

For many readers,most of what is presented in this chapter will constitute a review of material learned in a course in the fundamentals of economics.Students who are familiar with the application of elementary algebraic methods to the concepts of demand,supply,and the market process may proceed to Chapter 4 without any loss of continuity.

THE LAW OF DEMAND

The assumption of profit-maximizing behavior assumes that owners and managers know the demand for the firm’s good or service.The demand function asserts that there is a measurable relationship between the price that a company charges for its product and the number of units that buyers are willing and able to purchase during a specified time period.Economists refer to this behavioral relationship as the law of demand,which is sometimes called the first fundamental law of economics.

Definition:The law of demand states that the quantity demanded of a good or service is inversely related to the selling price, ceteris paribus (all other determinants remaining unchanged).

The term “law of demand”is actually a misnomer.As discussed in Chapter 1,laws are facts.Laws are assertions of fact.Laws predict events with certainty.By contrast,theories are probabilistic statements of cause

P

D

P1

P2

0 D

Q1 Q2

FIGURE 3.1 The demand curve. Q

and effect.The law of demand is a theory,as is invariably the case when human nature is involved.

Symbolically,the law of demand may be summarized as Q fP D = ( ) (3.1a)

and

dQ dP D < 0 (3.1b)

Equation (3.1a) states that QD,the quantity demanded of a good or service,is functionally related to the selling price P.Inequality (3.1b) asserts that quantity demanded and price are inversely related.This relationship is illustrated in Figure 3.1.The downward-sloping demand curve illustrates the inverse relationship between the quantity demanded of a good or service and its selling price.

The validity of the law of demand may be argued on the basis of common sense and simple observation.At a more sophisticated level,the validity of the law of demand may be argued on the basis of diminishing marginal utility and income and substitution effects.1

INCOME EFFECT

For most goods,the income effect asserts that as a product’s price declines (increases),an individual’s real income (purchasing power) increases (decreases).The increase in real purchasing power resulting from a fall in prices enables the individual to consume greater quantities of a commodity,while the opposite is true for an increase in prices.In other words,an

1 A formal derivation of the demand curve is presented in Appendix 3A.

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