Competition and consumer search costs can lead to price dispersion in an oligopoly. IO research has long identified the existence of search costs and estimated their distribution and is now beginning to study which consumers sit where in the distribution. This paper argues for a view of consumer protection and competition policy that considers distributional outcomes along with efficiency. We discuss the evidence on how consumer search varies over the income distribution and provide a literature review that summarizes research on (i) the search-income gradient; (ii) mechanisms for the gradient; and (iii) how search-based price discrimination can give rise to regressive price dispersion. Through our review, we collect evidence from a wide range of industries that shows that low-income consumers tend not to search. We then draw on research from IO, marketing, finance, urban, and behavioral economics for explanations as to why this pattern persists. Finally, we conclude that IO researchers have much to offer in identifying and quantifying the distributional impacts of market power, thereby contributing to current academic and policy debates on efficiency-equity trade-offs in policy design.

竞争和消费者搜索成本会导致寡头垄断的价格分散。IO 研究早就确定了搜索成本的存在并估计了它们的分布，现在开始研究哪些消费者在分布中的位置。本文主张考虑分配结果和效率的消费者保护和竞争政策观点。我们讨论了关于消费者搜索如何随收入分配变化的证据，并提供了一篇文献综述，总结了对 (i) 搜索收入梯度的研究；(ii) 梯度机制；(iii) 基于搜索的价格歧视如何导致回归价格分散。通过我们的审查，我们从广泛的行业收集了证据，表明低收入消费者往往不进行搜索。然后我们借鉴 IO 的研究，营销、金融、城市和行为经济学的解释为什么这种模式持续存在。最后，我们得出结论，IO 研究人员在识别和量化市场支配力的分配影响方面可以提供很多帮助，从而为当前关于政策设计中效率-股权权衡的学术和政策辩论做出贡献。