Theories of Liquidity By Dimitri Vayanos and

We survey the theoretical literature on market liquidity. The literature traces illiquidity, i.e., the lack of liquidity, to underlying market imperfections. We consider six main imperfections: participation costs, transaction costs, asymmetric information, imperfect competition, funding constraints, and search. We address three questions in the context of each imperfection: (a) how to measure illiquidity, (b) how illiquidity relates to underlying market imperfections and other asset characteristics, and (c) how illiquidity affects expected asset returns. We nest all six imperfections within a common, unified model, and use that model to organize the literature.