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This essay surveys the new monetarist approach to liquidity. Work in this literature strives for empirical and policy relevance, plus rigorous foundations. Questions include: What is liquidity? Is money essential in achieving desirable outcomes? Which objects can or should serve in this capacity? When can asset prices differ from fundamentals? What are the functions of commitment and collateral in credit markets? How does money interact with credit and intermediation? What can and should monetary policy do? The research summarized emphasizes the micro structure of frictional transactions, and studies how institutions like monetary exchange, credit arrangements, or intermediation facilitate the exchange process.

This essay surveys the literature on directed search and competitive search equilibrium, covering theory and a variety of applications. These models share features with traditional search theory, but also differ in important ways. They share features with general equilibrium theory, but with explicit frictions. Equilibria are often efficient, mainly because markets price goods plus the time required to get them. The approach is tractable and arguably realistic. Results are presented for finite and continuum economies. Private information and sorting with heterogeneity are analyzed. While emphasizing issues and applications, we also provide several hard-to-find technical results.

Search‐theoretic models of monetary exchange are based on explicit descriptions of the frictions that make money essential. However, tractable versions of these models typically make strong assumptions that render them ill suited for monetary policy analysis. We propose a new framework, based on explicit micro foundations, within which macro policy can be studied. The framework is analytically tractable and easily quantifiable. We calibrate the model to standard observations and use it to measure the cost of inflation. We find that going from 10 percent to 0 percent inflation is worth between 3 and 5 percent of consumption—much higher than previous estimates.

We study economies with adverse selection, plus the frictions in competitive search theory. With competitive search, principals post terms of trade (contracts), then agents choose where to apply, and they match bilaterally. Search allows us to analyze the effects of private information on both the intensive and extensive margins (the terms and probability of trade). There always exists a separating equilibrium where each type applies to a different contract. The equilibrium is unique in terms of payoffs. It is not generally efficient. We provide an algorithm for constructing equilibrium. Three applications illustrate the usefulness of the approach, and contrast our results with those in standard contract and search theory.

We develop a general equilibrium model where entrepreneurs finance random investment opportunities using trade credit, bank-issued assets, or currency. They search for bank funding in over-the-counter markets where loan sizes, interest rates, and down payments are negotiated bilaterally. The theory generates pass-through from nominal interest rates to real lending rates depending on market microstructure, policy, and firm characteristics. Higher banks’ bargaining power, for example, raises pass-through but weakens transmission to investment. Interest rate spreads arise from liquidity, regulatory, and intermediation premia and depend on policy described as money growth or open market operations.

We study the long-run relation between money (inflation or interest rates) and unemployment. We document positive relationships between these variables at low frequencies. We develop a framework where money and unemployment are modeled using explicit microfoundations, providing a unified theory to analyze labor and goods markets. We calibrate the model and ask how monetary factors account for labor market behavior. We can account for a sizable fraction of the increase in unemployment rates during the 1970s. We show how it matters whether one uses monetary theory based on the search-and-bargaining approach or on an ad hoc cash-in-advance constraint. (JEL E24, E31, E41, E43, E52)

This article argues that a pressing goal for macroeconomics is to incorporate financial considerations, but we need models with solid microfoundations. In particular, the use of assets in facilitating exchange, as well as different credit (or other financial) arrangements, should be outcomes of, not inputs to, theories. As a preview, I suggest that mainstream macro does a good job explaining many phenomena, and a financial crisis does not disprove such theory. But understanding crises requires better incorporating factors related to money, credit, banking, and liquidity. The approach called New Monetarist economics can help a lot in this regard.

We analyse dynamic general equilibrium models with more-or-less directed search by informed buyers and random search by uninformed buyers. This nests existing specifications and generates new insights. A quantitative application concerns the welfare cost of inflation, which is known to be quite high with pure random search and low with pure directed search. Our calibration implies the impact of inflation is fairly low, in part because, in addition to the usual costs, it provides benefits by more heavily taxing high-price sellers that inefficiently profit from exploiting the uninformed. Other applications analyse analytically and numerically changes in credit conditions and information.

We compare three market structures for monetary economies: bargaining (search equilibrium); price taking (competitive equilibrium); and price posting (competitive search equilibrium). We also extend work on the microfoundations of money by allowing a general matching technology and entry. We study how equilibrium and the effects of policy depend on market structure. Under bargaining, trade and entry are both inefficient, and inflation implies first-order welfare losses. Under price taking, the Friedman rule solves the first inefficiency but not the second, and inflation may actually improve welfare. Under posting, the Friedman rule yields the first best, and inflation implies second-order welfare losses.

We survey the literature on search-theoretic models of the labor market. We show how this approach addresses many issues, including the following: Why do workers sometimes choose to remain unemployed? What determines the lengths of employment and unemployment spells? How can there simultaneously exist unemployed workers and unfilled vacancies? What determines aggregate unemployment and vacancies? How can homogeneous workers earn different wages? What are the tradeoffs firms face from different wages? How do wages and turnover interact? What determines efficient turnover? We discuss various modeling choices concerning wage determination and the meeting process, including recent models of directed search.