Philipp Kircher

Directed Search with Multiple Job Applications

We develop an equilibrium directed search model of the labor market where workers can simultaneously apply for multiple jobs. Our main theoretical contribution is to integrate the portfolio choice problem faced by workers into an equilibrium framework. All equilibria of our model exhibit wage dispersion. Consistent with stylized facts, the density of wages is decreasing and higher wage firms receive more applications per vacancy. Unlike most models of directed search, the equilibria are not constrained efficient.

Sorting and Decentralized Price Competition

We investigate the role of search frictions in markets with price competition and how it leads to sorting of heterogeneous agents. There are two aspects of value creation: the match value when two agents actually trade and the probability of trading governed by the search technology. We show that positive assortative matching obtains when complementarities in the former outweigh complementarities in the latter. This happens if and only if the match-value function is root-supermodular, that is, its nth root is supermodular, where n reflects the elasticity of substitution of the search technology. This condition is weaker than the condition required for positive assortative matching in markets with random search.

Efficiency of Simultaneous Search

This paper presents an equilibrium labor search model in which workers can simultaneously apply to multiple firms to increase their search intensity. They observe firms’ wage postings before choosing where to apply. Owing to coordination frictions, a firm may not receive any applications; otherwise it is able to hire unless all its applicants have better offers. It is shown that the equilibrium converges to the efficient Walrasian outcome as application costs vanish. Even for nonnegligible application costs, the entry of firms, the search intensity, and the number of filled vacancies are constrained efficient. Wage dispersion is essential for constrained efficiency.

On the Game-Theoretic Foundations of Competitive Search Equilibrium

We provide a unified directed search framework with general production and matching specifications that encompass most of the existing literature. We prove the existence of subgame perfect Nash equilibria in pure firm strategies in a finite version of the model. We use this result to derive a more complete characterization of the equilibrium set for the finite economy and to extend convergence results as the economy becomes large to general production and matching specifications. The latter extends the microfoundations for the standard market utility assumption used in competitive search models with a continuum of agents to new environments.

An Equilibrium Model of the African HIV/AIDS Epidemic

Eleven percent of the Malawian population is HIV infected. Eighteen percent of sexual encounters are casual. A condom is used one quarter of the time. A choice-theoretic general equilibrium search model is constructed to analyze the Malawian epidemic. In the developed framework, people select between different sexual practices while knowing the inherent risk. The analysis suggests that the efficacy of public policy depends upon the induced behavioral changes and general equilibrium effects that are typically absent in epidemiological studies and small-scale field experiments. For some interventions (some forms of promoting condoms or marriage), the quantitative exercise suggests that these effects may increase HIV prevalence, while for others (such as male circumcision or increased incomes) they strengthen the effectiveness of the intervention. The underlying channels giving rise to these effects are discussed in detail.

Efficient Competition Through Cheap Talk: The Case of Competing Auctions

We consider a large market where auctioneers with private reservation values compete for bidders by announcing cheap‐talk messages. If auctioneers run efficient first‐price auctions, then there always exists an equilibrium in which each auctioneer truthfully reveals her type. The equilibrium is constrained efficient, assigning more bidders to auctioneers with larger gains from trade. The choice of the trading mechanism is crucial for the result. Most notably, the use of second‐price auctions (equivalently, ex post bidding) leads to the nonexistence of any informative equilibrium. We examine the robustness of our finding in various dimensions, including finite markets and equilibrium selection.

MARKET POWER AND EFFICIENCY IN A SEARCH MODEL

We build a theoretical model to study the welfare effects and resulting policy implications of firms’ market power in a frictional labor market. Our environment has two main characteristics: wages play a role in allocating labor across firms and there is a finite number of agents. We find that the decentralized equilibrium is inefficient and that the firms’ market power results in the misallocation of workers from the highto the low-productivity firms. A minimum wage forces the low-productivity firms to increase their wage, leading them to hire even more often thereby exacerbating the inefficiencies. Moderate unemployment benefits can increase welfare because they limit firms’ market power by improving the workers’ outside option.

Matching, Sorting, and the Distributional Effects of International Trade

We study the distributional consequences of trade in a world with two industries and two heterogeneous factors of production. Productivity in each production unit reflects the ability of the manager and the abilities of the workers, with complementarity between the two. We begin by examining the forces that govern the sorting of worker and manager types to industries and the matching of workers and managers within industries. We then consider how changes in relative output prices generated by changes in the trading environment affect sorting, matching, and the distributions of wages and salaries.

On the Difference between Social and Private Goods

Abstract Standard economic models have long been applied to choices over private consumption goods, but have recently been extended to incorporate social situations as well. We challenge the applicability of standard decision-theoretic models to social settings. In an experiment where choices affect the payoffs of someone else, we find that a large fraction of subjects prefer randomization over any of the deterministic outcomes. This tendency prevails whether the other party knows about the choice situation or not. Such randomization violates standard decision theory axioms that require that lotteries are never better than their best deterministic component. For conceptually similar choices in classical non-social situations, we do not find much evidence for such violations, suggesting the need for theories of uncertainty that are targeted to social settings.

Heterogeneous Firms in a Finite Directed Search Economy

We consider a directed search model for a finite economy with heterogeneous firms in two informational environments. In the first, the productivity of all firms is publicly observed. We prove existence of equilibria in pure posting strategies by firms and show that wage dispersion is driven by fundamentals. That is, more productive firms post higher wages and wage dispersion is absent when firms are homogeneous. When firms have heterogeneous productivities the equilibrium is not constrained efficient. In the second environment the productivity level of each firm is private information. The main results extend to this environment: Equilibria in pure strategies exist; strategies are increasing in productivity; and constrained efficiency does not obtain. When the productivity level of all firms is drawn from the same distribution, symmetric equilibria exist and the ranking of wages equals that of productivity.