We use an economic experiment to examine the impact of an ambiguous level of asymmetric information on the behavior of security dealers. Specifically, we distinguish three types of uncertainty with respect to informed trading: risk, compound risk, and ambiguity; for both a monopoly and a duopoly market setting. We find that dealer’s bidding behavior is less aggressive under an ambiguous level o...

Several studies document that past returns and past trading volume predict shortterm stock returns. This study considers two new variables: the past number of trades signed as purchase and sale. These variables also predict weekly US stock returns and contain information that is distinct from past returns and past trading volume. Combined trading strategies outperform strategies based on past r...

We investigate informed trading activity in equity options prior to the announcement of corporate mergers and acquisitions (M&A). For the target companies, we document pervasive directional options activity, consistent with strategies that would yield abnormal returns to investors with private information. This is demonstrated by positive abnormal trading volumes, excess implied volatility and ...

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We propose and estimate a structural model of daily stock market activity to test competing theories of trading volume. The model features informed rational speculators and uninformed agents who trade either to hedge endowment shocks or to speculate on perceived information. To identify the model parameters, we exploit enormous empirical variation in trading volume, market liquidity, and return...