Résumé en anglais

We empirically investigate the effect of option listing on the underlying stock pricing efficiency by examining the stock price duration dynamic. We use univariate tests and modified Log-ACD models that account for liquidity. Results indicate that option listing neither damages nor improves the underlying stock efficiency. However, they suggest that a new arrival of informed traders could occur during the trading day as a seasonal feature. We also find a decrease in informed trading for low volume stocks. Furthermore, Euronext and Liffe merger seems to have an impact on the duration process and on the informational content of underlying stocks.