Generic regularity of differentiated product oligopolies
证明在差异化产品寡头模型中，对于大多数经济环境，企业的最优反应函数在均衡附近是可微的，从而保证了比较静态分析的有效性，且纯策略均衡数量有限。
Abstract In oligopoly models with differentiated products, producers face a market demand function that reflects the preferences of consumers. However, typical assumptions on preferences place only weak restrictions on the shape of aggregate demand. This may result in profit functions that are not strictly quasiconcave, in best-reply correspondences that are not differentiable, and in equilibria that are not robust to perturbations. This paper establishes differentiability and robustness as a generic property: for an open, dense set of economies, best replies are differentiable in a neighborhood of equilibria, which is a precondition for comparative statics. All these economies have a finite number of equilibria in pure strategies.