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The Pacman Conjecture holds that durable goods monopolists have complete market power and so can exercise perfect price discrimination, thus extracting the total surplus.〔Coase versus Pacman: Who Eats Whom in the Durable Goods Monopoly? Author(s): Nils-Henrik Morch von der Fehr and Kai-Uwe Kuhn Source: The Journal of Political Economy, Vol. 103, No. 4, (Aug., 1995), pp. 785-812 Published by: The University of Chicago Press〕 This is in contrast to the Coase Conjecture which holds that a durable goods monopolist has ''no'' market power, and so price is equal to the competitive market price. In a December 1989 journal article〔Bagnoli, M., Salant, S.W., & Swierzbinski, J.E. "Durable-Goods Monopoly with Discrete Demand". ''The Journal of Political Economy'', 97.6 (December 1989), pp. 1459–1478. ((JSTOR ))〕 Mark Bagnoli, Stephen W. Salant, and Joseph E. Swierzbinski theorized that if each consumer could be relied upon to buy a good as soon as its price dipped below a certain point (with different consumers valuing goods differently, but all pursuing the same "get-it-while-you-can" strategy), then a monopolist could set prices very high initially and then "eat his way down the demand curve," extracting maximum profit in what Bagnoli et al. called "the Pacman strategy" after the voracious video-game character. Specifically, Bagnoli et al. state that "Pacman is a sequential best reply to get-it-while-you-can," a result they call "the Pacman Theorem". Their proof, however, relies strongly on the assumption that there is an infinite time horizon. ==Durable-goods monopolists and the Coase Conjecture== A durable-goods monopolist sells goods which are in finite supply and which last forever, (not depreciating over time). According to the Coase Conjecture, such a monopolist has no market power as it is in competition with itself; the more of the good it sells in period one the less it will be able to sell in future periods. Assuming marginal costs are zero. In the first period the monopolist will produce quantity (Q1) where marginal cost = marginal revenue and so extract the monopoly surplus. However, in the second period the monopolist will face a new residual demand curve (Q − Q1) and so will produce quantity where the new marginal revenue is equal to the marginal cost, which is at the competitive market price. There is then an incentive for consumers to delay purchase of the good as they realize that its price will decrease over time. If buyers are patient enough they will not buy until the price falls and so durable goods monopolists face a horizontal demand curve at the equilibrium price and so will have no market power. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pacman conjecture」の詳細全文を読む スポンサード リンク
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