北大ceer笔记8.ppt

Chapter Nine Buying and Selling Structure Endowments Budget constraints with endowments Net demands Labor supply Buying and Selling Trade involves exchange -- when something is bought something else must be sold. What will be bought? What will be sold? Who will be a buyer? Who will be a seller? Buying and Selling And how are incomes generated? How does the value of income depend upon commodity prices? How can we put all this together to explain better how price changes affect demands? Endowments The list of resource units with which a consumer starts is his endowment （禀赋）. A consumer’s endowment will be denoted by the vector (omega). Endowments E.g.states that the consumer is endowed with 10 units of good 1 and 2 units of good 2. Endowments E.g.states that the consumer is endowed with 10 units of good 1 and 2 units of good 2. What is the endowment’s value? For which consumption bundles may it be exchanged? Endowments p1=2 and p2=3 so the value of the endowment is Q: For which consumption bundles may the endowment be exchanged? A: For any bundle costing no more than the endowment’s value. Budget Constraints Revisited So, given p1 and p2, the budget constraint for a consumer with an endowment is The budget set is Budget Constraints Revisited Budget Constraints Revisited Budget Constraints Revisited Budget Constraints Revisited Budget Constraints Revisited Budget Constraints Revisited Budget Constraints Revisited Budget Constraints Revisited The constraintis That is, the sum of the values of a consumer’s net demands （净需求） is zero. Net Demands Suppose and p1=2, p2=3. Then the constraint is  If the consumer gross demands (毛需求）(x1*,x2*) = (7,4), then 3 good 1 units exchange for 2 good 2 units. Net demands are x1*- w1 = 7-10 = -3 andx2*- w2 = 4 - 2 = +2. Net Demands Net Demands Net Demands Net Demands Net Demands Net Demands Net Demands Labor Supply A worker