曼昆微观经济学(双学位).pptVIP

* * “Identical” means all firms have the same cost curves. Note: P1 is minimum AVC. At any price below P1, each firm will shut down, and market quantity supplied will equal zero. Hence, the market supply curve begins at price = P1 and Q = 10,000. * * Students often wonder why firms bother to stay in business if they make zero profit. The textbook gives a nice discussion of this, briefly summarized on this slide. * * That the LR market supply curve is horizontal at P = min ATC will become more clear shortly, when students see the SR and LR effects of an increase in demand. * * This slide replicates Figure 8 from the textbook. In edit mode, the text boxes in the top part of the slide appear to be on top of each other. But in slide-show mode, the text boxes display one at a time. If students did not previously understand why the LR market supply curve is horizontal, this slide may help. * * Here are two of the assumptions we made previously, when we began the process of deriving the LR market supply curve. * * The marginal firm is the firm that would exit the market if the price were any lower. * * Another example: There’s a limited amount of beachfront property. An expansion of the beach resort industry will bid up the price of such property, and raises costs in the industry. * * Recall from Chapter 7: a competitive market equilibrium is efficient. This chapter has shown why: P = MR under perfect competition, so P = MC in the competitive market equilibrium. Reviewing these concepts now sets the stage for the next few chapters, where firms with market power set their price above marginal cost, leading to market inefficiencies and a potential role for government intervention. * * This slide is “hidden” and will not display in your presentation. I have included it here in case you would like to substitute it for “Active Learning 2A.” The height of the rectangle is P – ATC, profit per unit. The width of the rectangle is Q, the n