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1、中级微观经济学参考书：Hal R. Varian. Intermediate Microeconomics, A Modern Approach. W. W. Norton & Company, Inc.1 BUDGET CONSTRAINTConsumer theory - how consumers buy their goods? Economists assume: consumers choose the best bundle of goods they can afford. Two aspects:-Consumers choose the most preferred goo
2、ds.-They are limited by economic condition.The Budget Constraint Consumption bundles: （消费束，商品组合）: a list of numbers of goods and services. X=(x1, x2, , x n,)In the case of two goods: good 1 and good 2: X = (x1, x2)Prices of goods: (p1, p2), The amount of money the consumer has to spend: m. The consu
3、mers affordable consumption bundles, (x1, x2) satisfyingp1x1 + p2x2 m.-The budget set of the consumer. good 2 m/p2 O m/p1 good 1The case of n goodsBudget constraint: p1x1 + p2x2+ pnxn m.Two Goods Are Often EnoughComposite good -take x2 as everything else, the dollars spent on other goods.For example
4、, x1: consumption of milk in quarts per month. Thus the budget constraint will take the form p1x1 + x2 m. Properties of the Budget SetBudget line（预算线）: p1x1 + p2x2 = m.Vertical intercept: m/p2Horizontal intercept: m/p1.Slope: p1/p2For the budget line:p1x1 + p2x2 = m.After a change in bundle (x1, x2)
5、:p1(x1+x1) + p2(x2+x2) = m. good 2 x2 x2x1 O x1 good 1Subtracting the first equation from the second gives p1x1 + p2x2 = 0.This gives Economic interpretation of slope:If the consumer changes his consumption of good 1 by x1, good 2 by x2, and keeps the money spent unchanged.Opportunity cost of consum
6、ing good 1- in order to consume more of good 1 you have to give up some consumption of good 2. Budget Line ChangesHow the Budget Line Changes when prices and incomes change?Change in income results in a parallel shift of the budget line.Intercepts m/p2 and m/p1 will change. Slope p1/p2 keeps unchang
7、ed. good 2 m/p2 O m/p1 good 1Changes in pricesIncreasing p1 will not change the vertical intercept, but p1/p2 will become larger. good 2 m/p2 O m/p1 good 1What happens to the budget line when we change the prices of good 1 and good 2 at the same time? Proportionally: (tp1)x1 + (tp2)x2 = m.What happe
8、ns to the budget line when we change the prices of good 1 and good 2 and the consumers income at the same time? Proportionally: (tp1)x1 + (tp2)x2 = tm. good 2 m/p2 O m/p1 good 1Some observations:If one price declines and all others stay the same, the consumer must be at least as well-off. If the con
9、sumers income increases and all prices remain the same, the consumer must be at least as well-off as at the lower incomeA perfectly balanced inflation cannot change anybodys optimal choice.2 PREFERENCESConsumer Preferences（消费者偏好）Consumer ranks consumption bundles by his satisfaction from use of good
10、s, irrelevant to the prices.The case of two goodsGiven any two consumption bundles, X=(x1, x2) and Y=(y1, y2), the consumer can rank them in one of three possible ways:(x1, x2) is strictly better than (y1, y2);(y1, y2) is strictly better than (x1, x2); (x1, x2) and (y1, y2) are indifferent.Two basic
11、 relations: strictly preferred（严格偏好于）, (x1, x2) (y1, y2): the consumer strictly prefers (x1, x2) to (y1, y2). : indifferent （无差异）(x1, x2) (y1, y2). the consumer is indifferent between (x1, x2) and (y1, y2). A composite relation: weakly preferred （弱偏好于）(x1, x2) (y1, y2): the consumer prefers (x1, x2)
12、 to (y1, y2) or is indifferent between (x1, x2) and (y1, y2).Assumptions about PreferencesAxioms about consumer preference (weakly preference):Complete（完备性）. Given any X-bundle and any Y-bundle, consumer can say that (x1, x2)(y1, y2), or (y1, y2)(x1, x2).Reflexive（反身性）. Consumer should say that any
13、bundle is at least as good as itself: (x1, x2)(x1, x2).Transitive 传递性）. If a consumer feels that (x1, x2)(y1, y2) and (y1, y2)(z1, z2) then he feels that (x1, x2)(z1, z2). Indifference CurvesWeakly preferred set: all of the consumption bundles that are weakly preferred to (x1, x2). Good 2 x2 O x1 Good 1Indifference curves（无差异曲线）: The boundary of weakly preferred set, the bundles for which the consumer is just indifferent to (x1, x2).Further assumptions Well-behaved preferences（良好的偏好）:Monotonicity （
