We examine the dynamic relation between return and volume of individual stocks. Using a simple model in which investors trade to share risk or speculate on private information, we show that returns generated by risk-sharing trades tend to reverse themselves, while returns generated by speculative trades tend to continue themselves. We test this theoretical prediction by analyzing the relation between daily volume and first-order return autocorrelation for individual stocks listed on the NYSE and AMEX. We find that the cross-sectional variation in the relation between volume and return autocorrelation is related to the extent of informed trading in a manner consistent with the theoretical prediction.

A model of competitive stock trading is developed in which investors are heterogeneous in their information and private investment opportunities and rationally trade for both informational and noninformational motives. I examine the link between the nature of heterogeneity among investors and the behavior of trading volume and its relation to price dynamics. It is found that volume is positively correlated with absolute changes in prices and dividends. I show that informational trading and noninformational trading lead to different dynamic relations between trading volume and stock returns. I.

This article studies the central role of the credit market. We show that the credit market facilitates optimal risk sharing by allowing less risk-averse investors to take on levered positions and consume more risk. The equilibrium amount behaves procyclically when aggregate consumption is low but countercyclically when it is high. The varying size of the credit market modifies the amount of risk sharing, which in turn influences asset prices such as expected stock returns, stock return volatility, and the term structure of interest rates. Our article provides a frictionless benchmark for the role and the behavior of the credit market. The Author 2012. Published by Oxford University Press on behalf of The Society for Financial Studies. All rights reserved. For Permissions, please e-mail: [email protected]., Oxford University Press.

"We examine the implications of portfolio theory for the cross-sectional behavior of equity trading volume. Two-fund separation theorems suggest a natural definition for trading activity: share turnover...We find strong evidence against two-fund separation, and a principal-components decomposition suggests that turnover is well approximated by a two-factor linear model" -- Abstract.

We develop a model of trading volume when agents have different valuation and face transaction costs. In particular, the differential valuation is induced by differential tax status which generates trading around the distribution of cash dividends. Our model predicts that trading volume is negatively affected by idiosyncratic risk of dividend-paying stocks. Volume is negatively affected by the systematic risk of these stocks only in the presence of transaction costs.Journal of Economic LiteratureClassification Numbers: G11, G12, H20.

This paper represents an equilibrium model for the demand and supply of liquidity and its impact on asset prices and welfare. We show that, when constant market presence is costly, purely idiosyncratic shocks lead to endogenous demand of liquidity and large price deviations from fundamentals. Moreover, market forces fail to lead to efficient supply of liquidity, which calls for potential policy interventions. However, we demonstrate that different policy tools can yield different efficiency consequences. For example, lowering the cost of supplying liquidity on the spot (e.g., through direct injection of liquidity or relaxation of ex post margin constraints) can decrease welfare while forcing more liquidity supply (e.g., through coordination of market participants) can improve welfare.

We analyze how asymmetric information and imperfect competition affect liquidity and asset prices. Our model has three periods: Agents are identical in the first, become heterogeneous and trade in the second, and consume asset payoffs in the third. We show that asymmetric information in the second period raises ex ante expected asset returns in the first, comparing both to the case where all private signals are made public and to that where private signals are not observed. Imperfect competition can instead lower expected returns. Each imperfection can move common measures of illiquidity in opposite directions.

In this paper, we develop an equilibrium model for stock market liquidity and its impact on asset prices when constant market presence is costly. We show that even when agents' trading needs are perfectly matched, costly market presence prevents them from synchronizing their trades and hence gives rise to endogenous order imbalances and the need for liquidity. Moreover, the endogenous liquidity need, when it occurs, is characterized by excessive selling of significant magnitudes. Such liquidity-driven selling leads to market crashes in the absence of any aggregate shocks. Finally, we show that illiquidity in the market leads to high expected returns, negative and asymmetric return serial correlation, and a positive relation between trading volume and future returns. We also propose new measures of liquidity based on its asymmetric impact on prices and demonstrate a negative relation between these measures and expected stock returns.

This article develops a multiperiod rational expectations model of stock trading in which investors have differential information concerning the underlying value of the stock. Investors trade competitively in the stock market based on their private information and the information revealed by the market-clearing prices, as well as other public news. We examine how trading volume is related to the information flow in the market and how investors' trading reveals their private information.