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1、Chapter Three,Preferences 消费者偏好,Where Are We in the Course?,We are studying the 1st of the three blocks of microeconomics: Consumer behavior, production theory, and market equilibrium Within the 1st block, we are working on the 2nd of the three components: choice set, preference, and consumer demand
2、,What Do We Mean by Preference? (偏好),It refers to the ordered relationship among alternative choices given by an economic agent. In most economic literature, consumer preference is treated as the ultimate exogenous element.,Notations,denotes strict preference; denotes indifference; denotes weak pref
3、erence;,p,Preference Relations,x y and y x imply x y. x y and (not y x) imply x y.,p,Assumptions about Preference Relations,Completeness: For any two bundles x and y it is always possible to make the statement that either x y or y x.,Assumptions about Preference Relations,Reflexivity: Any bundle x i
4、s always at least as preferred as itself; i.e. x x.,Assumptions about Preference Relations,Transitivity: Ifx is at least as preferred as y, andy is at least as preferred as z, thenx is at least as preferred as z; i.e. x y and y z x z.,Indifference Curves无差异曲线 (或,无差异集),Take a reference bundle x. The
5、set of all bundles equally preferred to x is the indifference curve containing x; the set of all bundles y x. Since an indifference “curve” is not always a curve a better name might be an indifference “set”.,Indifference Curves,x2,x1,x”,x”,x x” x”,x,Indifference Curves,x2,x1,z x y,p,p,x,y,z,Indiffer
6、ence Curves,x2,x1,x,All bundles in I1 are strictly preferred to all in I2.,y,z,All bundles in I2 are strictly preferred to all in I3.,I1,I2,I3,Indifference Curves,x2,x1,WP(x), the set of bundles weakly preferred to x.,WP(x) includes I(x).,x,I(x),Indifference Curves,x2,x1,SP(x), the set of bundles st
7、rictly preferred to x, does not include I(x).,x,I(x),Indifference Curves Cannot Intersect ! (不相交!),x2,x1,x,y,z,I1,I2,From I1, x y. From I2, x z. Therefore y z.,Indifference Curves Cannot Intersect,x2,x1,x,y,z,I1,I2,From I1, x y. From I2, x z. Therefore y z. But from I1 and I2 we see y z, a contradic
8、tion.,p,Slopes of Indifference Curves,When more of a commodity is always preferred, the commodity is a good. If every commodity is a good then indifference curves are negatively sloped.,Slopes of Indifference Curves,Better,Worse,Good 2,Good 1,Two goodsa negatively sloped indifference curve.,Slopes o
9、f Indifference Curves,If less of a commodity is always preferred then the commodity is a bad.,Slopes of Indifference Curves,Better,Worse,Good 2,Bad 1,One good and onebad a positively sloped indifference curve.,Extreme Cases of Indifference Curves; Perfect Substitutes,If a consumer always regards uni
10、ts of commodities 1 and 2 as equivalent, then the commodities are perfect substitutes and only the sum of the two commodities in bundles determines their preference rank-order.,Extreme Cases of Indifference Curves; Perfect Substitutes,x2,x1,8,8,15,15,Slopes are constant at - 1.,I2,I1,Bundles in I2 a
11、ll have a totalof 15 units and are strictly preferred to all bundles in I1, which have a total of only 8 units in them.,Extreme Cases of Indifference Curves; Perfect Complements,If a consumer always consumes commodities 1 and 2 in fixed proportion (e.g. one-to-one), then the commodities are perfect
12、complements and only the number of pairs of units of the two commodities determines the preference rank-order of bundles.,Extreme Cases of Indifference Curves; Perfect Complements,x2,x1,I2,I1,45o,5,9,5,9,Since each of (5,5), (5,9) and (9,5) contains 5 pairs, each is less preferred than the bundle (9
13、,9) which contains 9 pairs.,Preferences Exhibiting Satiation,A bundle strictly preferred to any other is a satiation point or a bliss point. What do indifference curves look like for preferences exhibiting satiation?,Indifference Curves Exhibiting Satiation,x2,x1,Better,Better,Better,Satiation(bliss
14、)point,Indifference Curves for Discrete Commodities,A commodity is infinitely divisible if it can be acquired in any quantity; e.g. water or cheese. A commodity is discrete if it comes in unit lumps of 1, 2, 3, and so on; e.g. aircraft, ships and refrigerators.,Indifference Curves for Discrete Commo
15、dities (study this yourself),Suppose commodity 2 is an infinitely divisible good (gasoline) while commodity 1 is a discrete good (aircraft). What do indifference “curves” look like?,Indifference Curves With a Discrete Good (study this yourself),Gas-oline,Aircraft,0,1,2,3,4,Indifference “curves”are c
16、ollections ofdiscrete points.,Well-Behaved Preferences,A preference relation is “well-behaved” if it is monotonic and convex. Monotonicity: More of any commodity is always preferred (i.e. no satiation and every commodity is a good).,Well-Behaved Preferences,Convexity (凸性): Mixtures of bundles are (at least weakly) prefe
