The only Dance in Town: Unique Equilibrium in a Generalized Model of Price Competition*
研究了一个涵盖多种经典情形的价格竞争模型，发现只有当部分消费者恰好比较两个价格时，才存在唯一的对称混合策略均衡；否则存在无数非对称均衡。
We study a model of simultaneous price competition that subsumes many employed in the literature over the last several decades. Firms sell a homogeneous good to consumers characterized by the number of prices they (exogenously) consider. We show there is a unique equilibrium if and only if some consumers consider exactly two prices. The equilibrium is in symmetric mixed strategies. When no consumer considers exactly two prices, there is, in addition, an uncountable infinity of asymmetric equilibria. Our results show that the paradigm generically produces a unique equilibrium, and only the commonly sought symmetric equilibrium is robust to perturbations in consumer behavior.