We introduce dynamic learning in the static search-theoretic framework of imperfect competition of Butters (1977), Varian (1980) and Burdett and Judd (1983). We consider two forms of learning: memory and word of mouth. In the model with memory, long-lived buyers not only learn about some new sellers in every period, but they also remember some of the sellers about which they learned in the past. In the model with word of mouth, short-lived buyers not only learn about sellers through search, but they also learn about sellers by talking to previous buyers, which refer them to the best seller of which they are aware. Both models are tractable. We establish the existence and uniqueness of equilibrium and characterize the dynamics of the product market. Memory increases the quantity of information available to buyers and, for this reason, leads to higher concentration and more competition over time for all sellers. Word of mouth increases the quality of information available to buyers and leads to higher concentration over time, but it does not increase competition for all sellers. With word of mouth, the dynamics of competition are heterogeneous across sellers and depend on a seller's popularity. For different sellers, competition and prices may be increasing, decreasing, or non-monotonic over time.

@article{Mangin_Menzio_Learning,
  title={Private and social learning in frictional product markets},
  author={Mangin, Sephorah and Menzio, Guido},
  journal = {Working paper},
  year={2024}
}

Equilibrium price dispersion for identical goods can arise from dispersion in the effective competition for each buyer, i.e. dispersion in the number of price quotes a buyer obtains or in the number of sellers in a buyer's choice set. We call this competitive dispersion. This paper studies the effects of competitive dispersion on equilibrium markups and price dispersion in a Burdett-Judd search-theoretic model of imperfect competition. We find that greater competitive dispersion can either increase or decrease the aggregate markup, depending on the degree of competition. Surprisingly, greater competitive dispersion does not always increase price dispersion. Equilibrium markups and price dispersion are constrained efficient if and only if the search technology is Poisson, which minimizes competitive dispersion but not necessarily price dispersion. We apply our results to the labor market and find that greater competitive dispersion can either increase or decrease both the average wage and wage dispersion.

@article{Mangin_CompetitiveDispersionMarkups,
  title={Competitive Dispersion, Price Dispersion, and Markups},
  author={Mangin, Sephorah},
  journal = {Working paper},
  year={2026}
}

We study the effects of competition on nonlinear pricing in a competitive search model where the distribution of buyer types is endogenous due to consumer choice. In the first stage (i.e. competitive search), sellers compete by offering price-quantity schedules that attract buyers to their submarket. In the second stage (i.e. imperfect competition), buyers meet a finite number of sellers within a submarket and choose a seller from within their multilateral meeting. The type of a consumer is their private valuation of their chosen seller's good. The endogenous distribution of types depends on the distribution of valuations, the degree of competition, and properties of the search technology (i.e. the distribution of the number of sellers a buyer meets). We find that greater competition decreases the extent of nonlinear pricing and reduces the quantity distortions. In the competitive limit, the effects of private information are eliminated.

@article{Mangin_CCNP,
  author = {Sephorah Mangin},
  title = {Consumer choice and nonlinear pricing in competitive search equilibrium},
  journal = {Working paper},
  year = {2025}
}

Does personalized pricing benefit or harm consumers? We show that the impact of personalized pricing depends on the degree of competitive dispersion. We consider an environment where the number of competing firms (i.e. the size of a consumer's choice set) varies across consumers. This variation may be due to either search frictions or consumer heterogeneity. An increase in competitive dispersion is a mean-preserving spread in the competitive distribution (i.e. the distribution across consumers of the number of competing firms). If competitive dispersion is low, personalized pricing benefits consumers and harms firms (relative to uniform pricing). However, if competitive dispersion is sufficiently high, we find that personalized pricing can harm consumers and benefit firms.

@article{Mangin_PPCD,
  author = {Sephorah Mangin},
  title = {Personalized pricing and competitive dispersion},
  journal = {Working paper},
  year = {2026}
}