We construct our measure of daily realized volatility for the S&P 500 index using
high-frequency futures data. S&P 500 index futures trade on the Chicago Mercantile
Exchange (CME) on the trading
oor from 8:30AM to 3:15PM (Eastern Standard
Time minus 1 hour, EST-1). Since January 3, 1994, these contracts also trade
overnight on GLOBEX, the electronic trading system of the CME, from 3:30PM to
8:00AM (8:15AM from February 26, 1996, onwards). As a result, S&P 500 futures
trade almost round the clock, providing a similar opportunity to construct realized