【正文】 $30,000 $15,000 14 D4 D6 D8 Demand Pure Price Effect Snob Effect Net Effect 72 Chapter 1 Network Externalities and the Demands for Computers and Fax Machines ? Examples of Positive Feedback Externalities ? Mainframe puters: 1954 1965 ? Microsoft Windows PC operating system ? Faxmachines and 73 Chapter 1 Empirical Estimation of Demand ? The most direct way to obtain information about demand is through interviews where consumers are asked how much of a product they would be willing to buy at a given price. 74 Chapter 1 Empirical Estimation of Demand ? Problem ? Consumers may lack information or interest, or be mislead by the interviewer. 75 Chapter 1 ? In direct marketing experiments, actual sales offers are posed to potential customers and the responses of customers are observed. Empirical Estimation of Demand 76 Chapter 1 ? The Statistical Approach to Demand Estimation ? Properly applied, the statistical approach to demand estimation can enable one to sort out the effects of variables on the quantity demanded of a product. ?“Leastsquares” regression is one approach. Empirical Estimation of Demand 77 Chapter 1 Year Quantity (Q) Price (P) Ine(I) Demand Data for Raspberries 1988 4 24 10 1989 7 20 10 1990 8 17 10 1991 13 17 17 1992 16 10 17 1993 15 15 17 1994 19 12 20 1995 20 9 20 1996 22 5 20 78 Chapter 1 ? Assuming only price determines demand: ? Q = a bP ? Q = Empirical Estimation of Demand 79 Chapter 1 Estimating Demand Quantity Price 0 5 10 15 20 25 15 10 5 25 20 d1 d2 d3 D D represents demand if only P determines demand and then from the data: Q= 80 Chapter 1 Estimating Demand Quantity Price 0 5 10 15 20 25 15 10 5 25 20 D d1 d2 d3 d1, d2, d3 represent the demand for each ine level. Including ine in the demand equation: Q = a bP + cI or Q = .49P + .81I Adjusting for changes in ine 81 Chapter 1 ? For the demand equation: Q = a bP ? Elasticity: Empirical Estimation of Demand Estimating Elasticities )/()/)(/( QPbQPPQE P ?????82 Chapter 1 ? Assuming: Price ine elasticity are constant ? The isoelastic demand = ? The slope, b = price elasticity of demand ? Constant, c = ine elasticity Empirical Estimation of Demand Estimating Elasticities )log()log()log( IcPbaQ ???83 Chapter 1 ? Using the Raspberry data: ? Price elasticity = (Inelastic) ? Ine elasticity = Empirical Estimation of Demand Estimating Elasticities )log()log()log( IPQ ????84 Chapter 1 ? Substitutes: b2 is positive ? Complements: b2 is negative Empirical Estimation of Demand Estimating Complements and Substitutes )log(log)log()log( 22 IcPbPbaQ ????85 Chapter 1 ? What Do You Think? ? Are Grape Nuts Spoon Size Shredded Wheat good substitutes? The Demand for ReadytoEat Cereal 86 Chapter 1 ? Answer ? Estimated demand for Grape Nuts (GN) ?Price elasticity = ?Ine elasticity = ?Cross elasticity = The Demand for ReadytoEat Cereal )log(014.)log()log()log(SWGNGN PIPaQ ????87 Chapter 1 Summary ? Individual consumers’ demand curves for a modity can be derived from information about their tastes for all goods and services and from their budget constraints. ? Engel curves describe the relationship between the quantity of a good consumed and ine. 88 Chapter 1 Summary ? Two goods are substitutes if an increase in the price of one good leads to an increase in the quantity demanded of the other. They are plements if the quantity demanded of the other declines. 89 Chapter 1 Summary ? Two goods are substitutes if an increase in the price of one good leads to an increase in the quantity demanded of the other. They are plements if the quantity demanded of the other declines. ? The effect of a price change on the quantity demanded can be broken into a substitution effect and an ine effect. 90 Chapter 1 Summary ? The market demand curve is the horizontal summation of the individual demand curves for all consumers. ? The percent change in quantity demanded that results from a one percent change in price determines elasticity of demand. 91 Chapter 1 Summary ? There is a work externality when one person’s demand is affected directly by the purchasing decisions of other consumers. ? A number of methods can be used to obtain information about consumer demand. 92 Chapter 1 End of Lecture 3 Individual and Market Demand 93 Chapter 1 演講完畢，謝謝觀看！