How does short selling affect liquidity in financial markets?

The paper seeks to determine whether short selling increases or decreases liquidity in U.S. equity markets. On one hand, prior research indicates that short sellers may act, at times, as liquidity providers. On the other hand, other research in market microstructure argues that spreads will widen in the presence of informed traders - a classification generally given to short sellers. Results from a series of new, multivariate time-series tests show that exogenous shocks to short selling activity generally lead to a widening of bid-ask spreads in smaller-cap stocks. The results, however, do not hold for larger-cap stocks.