Kenneth R. Ahern is the Dean’s Associate Professor in Business Administration at the University of Southern California. This post is based on his recent paper.
Trading by investors who have material, non-public information is of first-order importance to liquidity providers, stock market operators, and securities market regulators. Liquidity providers, such as market makers and institutional investors, worry that an informed trader will take advantage of their lack of information. Operators of stock markets worry that the presence of informed investors will drive uninformed investors out of the market. Regulators worry that an unfair advantage by some investors will impair equal access to equity markets.
Though many market participants worry about the presence of informed trading, there is little credible evidence on the validity of existing empirical proxies to identify periods of informed trading, such as bid-ask spreads, Kyle’s lambda, and trade order imbalances. Though these proxies are theoretically grounded, they remain largely untested. This is because validating the proxies requires the rare opportunity to directly observe informed trading.
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