Directed Search and Optimal Production

I consider a model of directed search in which strategic sellers advertise general trading mechanisms. A mechanism determines the number of buyers that will get served and the side payments as a function of ex post realized demand. After observing these advertisements buyers simultaneously visit exactly one seller. Each buyer’s expected utility depends on the visiting decisions of other buyers. This dependence becomes especially interesting since the buyers cannot coordinate their visiting strategies. Despite the presence of strategic interaction among the sellers all symmetric equilibria are constrained efficient but not payoff equivalent. Therefore, authorities should intervene in this type of market to redistribute surplus and not to improve efficiency. As markets grow infinitely large all equilibria yield the same profit. For the large market case I provide conditions under which only a very simple class of mechanisms is posted in equilibrium.directed search, efficiency, multiplicity of equilibrium

Asset Liquidity and International Portfolio Choice

We study optimal portfolio choice in a two-country model where assets represent claims on future consumption and facilitate trade in markets with imperfect credit. Assuming that foreign assets trade at a cost, agents hold relatively more domestic assets. Consequently, agents have larger claims to domestic over foreign consumption. Moreover, foreign assets turn over faster than domestic assets because the former have desirable liquidity properties, but represent inferior saving tools. Our mechanism offers an answer to a long-standing puzzle in international finance: a positive relationship between consumption and asset home bias coupled with higher turnover rates of foreign over domestic assets.

Unemployment insurance and optimal taxation in search models of the labor market

In many search models of the labor market, unemployment insurance (UI) is conveniently interpreted as the value of leisure or home production and is, therefore, treated as a parameter. However, in reality, UI has to be funded through taxation that might be distortionary. In this paper, I analyze the welfare implications of different taxation systems within two equilibrium models of unemployment: random search and directed search. In a random search model without taxes, efficiency is typically not achieved, unless the so-called Hosios condition is satisfied. If the bargaining power of firms is large, a lump-sum tax can discourage firms from entering and improve welfare. In a directed search model without taxes, constrained efficiency is always achieved. Since firms direct workers to apply to them by posting wages, raising UI funds in a lump-sum manner always distorts the efficient allocation, as it gives firms an incentive to be excessively aggressive in their attempt to maximize the probability of filing up their vacancies. I discuss two ways through which this externality can be internalized and efficiency can be re-established

Directed search and the Bertrand paradox

I study a directed search model of oligopolistic competition, extended to incorporate general capacity constraints, congestion effects, and pricing based on ex-post realized demand. I show that as long as any one of these ingredients is present, the Bertrand paradox will fail to hold. Hence, I argue that, despite the emphasis that has been placed by the literature on sellers' capacity constraints as a resolution to the paradox, the existence of such constraints is only a subcase of a general class of environments where the paradox fails. More precisely, Bertrand's paradox will not arise whenever the buyers' expected utility from visiting a specific seller is decreasing in that seller's realized demand

Monetary policy, asset prices, and liquidity in over-the-counter markets

We revisit a traditional topic in monetary economics: the relationship between asset prices and monetary policy. We study a model in which money helps facilitate trade in decentralized markets, as in Lagos andWright (2005), and real assets are traded in an over-the-counter (OTC) market, as in Duffie, Gˆarleanu, and Pedersen (2005). Agents wish to hold liquid portfolios, but liquidity comes at a cost: inflation. The OTC market serves as a secondary asset market, in which agents can rebalance their positions depending on their liquidity needs. Hence, a contribution of our paper is to provide a micro-founded explanation of the assumption that different investors have different valuations for the same asset, which is the key for generating gains from trade in the Duffie et al framework. In equilibrium, assets can be priced higher than their fundamental value because they help agents avoid the inflation tax

A search-theoretic model of the term premium

A consistent empirical feature of bond yields is that term premia are, on average, positive. That is, investors in long term bonds receive higher returns than investors in similar (i.e.\ same default risk) shorter maturity bonds over the same holding period. The majority of theoretical explanations for this observation have viewed the term premia through the lens of the consumption based capital asset pricing model. In contrast, we harken to an older empirical literature which attributes the term premium to the idea that short maturity bonds are inherently more liquid. The goal of this paper is to provide a theoretical justification of this concept. To that end, we employ a model in the tradition of modern monetary theory extended to include assets of different maturities. Short term assets always mature in time to take advantage of random consumption opportunities. Long term assets do not, but agents may liquidate them in a secondary asset market, characterized by search-and-bargaining frictions a la Duffie, Garleanu, and Pedersen (2005). In equilibrium, long term assets have higher rates of return to compensate agents for their relative lack of liquidity. Consistent with empirical findings, our model predicts a steeper yield curve for assets that trade in less liquid secondary markets

Mixing and condensation in a wet granular medium

We have studied the effect of small amounts of added liquid on the dynamic behavior of a granular system consisting of a mixture of glass beads of two different sizes. Segregation of the large beads to the top of the sample is found to depend in a nontrivial way on the liquid content. A transition to viscoplastic behavior occurs at a critical liquid content, which depends upon the bead size. We show that this transition can be interpreted as a condensation due to the hysteretic liquid bridge forces connecting the beads, and provide the corresponding phase diagram.Comment: submitted to PR