Ji-Chai Lin, Michael S. Rozeff, Price Adjustment Delays and Arbitrage Costs: Evidence from the Behavior of Convertible Preferred Prices, The Journal of Financial and Quantitative Analysis, Vol. 30, No. 1 (Mar., 1995), pp. 61-80

We examine stock price behavior in response to initial coverage, buy recommendations that are pre-released to important clients before the stock market opens, and find a strong positive valuation effect at the open. On average, it takes five minutes of trading for NYSE/AMEX stocks and 15 minutes for NASDAQ stocks to reflect the private information contained in these analyst recommendations, so when informational asymmetry is high, the centralized call market is more efficient than a competitive, but fragmented dealer market. Public news release leaves share prices unaltered. Overall, competition among informed traders causes private information to be rapidly incorporated into stock prices.

A vector autoregressive (VAR) model is used to examine the relation between aggregate insider transactions and stock market returns. Consistent with the extant literature, there is some predictive content associated with aggregate insider transactions, but its magnitude is slight. In contrast, market returns have substantial influence on the aggregate purchases and sales of corporate insiders. The findings suggest that: 1) the degree of mispricing observed by insiders is small; 2) very little of the mispricing is associated with unanticipated macroeconomic factors; and 3) investors cannot use aggregate insider transactions to profitably predict future market returns over the following eight weeks.