Oligopolistic Fixed-Price Equilibria and the Number of Firms
研究了寡头垄断行业中企业数量如何影响固定价格均衡的形成，发现当企业数量超过一定阈值时，低需求时期的合谋可以维持高需求时期的价格水平。
In this note, we examine one of the potential macroeconomic explanations of cyclically inflexible prices, discussed previously by Stiglitz (1984), i.e., that of collusive behavior by oligopolists.1 We consider an industry with a fixed number of identical firms with linear cost functions that face a linear demand curve shifting stochastically between high- and low-demand periods. Firms are taken to behave in a standard Nash-Cournot fashion in high-demand periods. We then derive the conditions under which collusion in low-demand periods, so as to keep the uniform market price at its high-demand level, constitutes a equilibrium of the discounted, infinitely repeated market game. The (credible) threat which deters deviations from the fixedprice solution is that all firms will revert to their symmetric Nash (N) strategies once any one firm is caught deviating from its allowed output under the fixed-price (F) strategy. Our idea is that keeping prices fixed in this way may constitute a focal point, in Schelling's (1960) terminology, which aids the coordination of firms' collusive strategies.2 With perfect enforcement (i.e., any deviation from the collusive strategy is discovered in a low-demand period), which is assumed in Section II, we show that contrary to common belief, such an F equilibrium is enforced whenever the number of firms exceeds a certain minimum level. The intuition behind this result is that the equilibrium high-demand price is a decreasing function of the number of firms, making myopic quantity deviations from the symmetric F strategy more tempting in low-demand periods, the fewer firms there are. 'The idea that oligopolistic behavior may lead to inflexible or administered prices has a long tradition in economics, going back to Means (1935), Stigler (1962) and Scherer (1970). 2 An approach related to ours is Rotemberg & Saloner (1986), who showed that fixed prices may arise under oligopolistic price competition, when price wars are more likely under high demand.