Average delta hedged returns for Standard & Poor's 500 index options are large: −0.7% per day. When we decompose these option returns into intraday and overnight components, average close-to-open returns are −1% per day and open-to-close returns are positive, 0.3%. A similar return pattern holds for all maturity and moneyness categories and equity options. These positive intraday returns are particularly difficult to explain. However, our results are consistent with option prices’ failing to account for the well-known fact that stock volatility is substantially higher intraday than overnight. These findings help explain price formation in the options market.

Conventional estimates of the costs of taking liquidity in options markets are large. Nonetheless, options trading volume is high. We resolve this puzzle by showing that options price changes are predictable at high frequency, and many traders time executions by buying (selling) when the option fair value is close to the ask (bid). Effective spreads of traders who time executions are less than 40% of the size of conventional measures, and the overall average effective spread is one-quarter smaller than conventional estimates. Price impact measures are also affected. These findings alter conclusions about the after-cost profitability of options trading strategies.