While algorithmic trading now dominates financial markets, some exchanges continue to use human floor traders. On March 23, 2020 the NYSE suspended floor trading because of COVID-19. Using a difference-in-differences analysis, we find that floor traders are important contributors to market...

We investigate institutional trading of American Depositary Receipts (ADRs) around ex-dividend dates motivated by recent concerns of abusive practices of ADR pre-releases and illegal refunds of dividend withholding taxes. Using data on US stocks, foreign stocks, and ADRs from 1999 to 2014, we...

We propose a new approach to measuring informed trading in individual securities based on a portfolio optimization model for investors facing information and liquidity shocks. These shocks induce speculative and liquidity-motivated order flow, taking into account the price impact of trading. The...

Using limit order books across all U.S. exchanges, we show that while liquidity for small orders (e.g., the quoted and effective spreads) decreases, liquidity for large orders (e.g., the cumulative depth and the price impact of multiple trades) improves after the implementation of the Tick Size...

The capital asset pricing model (CAPM) performs poorly overall as market risk (beta) is weakly related to 24-hour returns. This is because stock prices behave very differently with respect to their sensitivity to beta when markets are open for trading versus when they are closed. Stock returns...

We propose a portfolio optimization approach to identifying private information. In our model, investors are exposed to liquidity and private information shocks and optimize their trading across stocks taking into account price impact (Kyle's Lambda). We obtain a very simple expression for a...