平狄克 微觀經(jīng)濟(jì)學(xué) 第七版 課件 第二章

1、 14 How many indifference curves can we draw? Can two indifference curves cross? 31 32 Marginal Rate of Substitution Clothing U2 U1 A B U2 D U1 Food 33 Definition: the maximum amount of a good that a consumer is willing to give up in order to obtain one additional unit of another good 34 Slope of In

2、difference Curve Clothing MRS = slope of IC Clothing 16 14 12 10 8 6 4 2 1 -6 A 16 14 12 -6 A MRS = 6 MRS = C F 1 -4 B D 1 -2 1 -1 1 10 8 6 E G Food 35 1 -4 B MRS = 2 D 1 -2 1 -1 1 E G Food 36 4 2 1 2 2 3 4 5 3 4 5 6 Convex Indifference Curves Often, we see Diminishing Marginal Rate of Substitution

3、along an indifference curve (why? MRS = slope of IC = ratio of MUs Diminishing MRS <=> convex indifference curves Coca Cola Perfect Substitutes 4 3 2 1 Pepsi 38 0 37 1 2 3 4 Perfect Complements Left Shoes NOT Goods Bads: the reverse of goods things for which less is preferred to more e.g. poll

4、ution, work 4 3 2 1 0 1 2 3 4 Right Shoes 39 Neuters: neither a good nor a bad things you do not care having or not having MU = 0 40 Utility Function A formula that assigns a level of utility to each consumption bundle E.g. A utility function on food and clothing is U(F,C = F + 2C How to draw indiff

5、erence curves to represent this utility function? What is the MRS at a particular bundle on an indifference curve? 41 Utility Function E.g. U(F,C = FC How to draw the indifference curves? What is the MRS? How about U(F,C = 2FC ? 42 7 Ordinal and Cardinal Utility Function Ordinal Utility Function uti

6、lity levels are only meaningful up to the point that they could be used to rank different bundles indicates whether one bundle is better than another Ordinal and Cardinal Utility Function Analyses in economics usually require only ordinal utility functions weaker assumptions => more general suffi

7、cient to explain many behavior Cardinal Utility Function utility function describing the extent to which one bundle is preferred to another indicates whether and how much one bundle is better than another 43 With ordinal utility functions, actual units of utilities are not important certain transfor

8、mations of a utility function still represent the same preferences Direction of preference and indifference curves 44 How about doubling all utility levels? Clothing Budget Constraint Budget constraint limits an individuals ability to consume since goods and services have to be paid for with a limit

9、ed income A budget line indicates all combinations of two goods for which total spending equals total income e.g. 15 10 U3 = 100 5 U2 = 50 U1 = 25 Food 0 5 10 15 45 PF F + PC C = I Assume income of 80, PF = 1 and PC = 2 46 Budget Line Clothing Budget Line What is the slope of the budget line? ratio

10、of prices of the two goods ratio of which price to which other price? (I/PC = 40 30 A B 10 D 20 E How would the budget line change with a change in income? a change in the price of one good? G 80 = (I/PF Food 47 48 20 10 0 20 40 60 8 Budget Line Clothing Budget Line Clothing (income changes (price c

11、hanges 80 60 40 40 20 0 L3 (I =$40 L3 L1 (I = $80 L2 (I = $160 L1 (PF = 1 80 L2 (PF = 1/2 120 160 Food 50 Food 49 (PF = 2 40 40 80 120 160 Purchasing Power What if both prices are half as before? The ability of an income to exchange for goods and services Depends on the amount of income and prices of goods When there is inflation, how would the purchasing power of a fixed amount of income change over time? 51 52 Exercises for Review (Note: these are not part of your assign