Open volume and time to open on option-expiration days

We examine the volume and time to open for stocks on option-expiration Fridays. We show that previous findings of abnormal daily volume on option-expiration Fridays can be largely explained by the large volume of trading in the batch opening for stocks that trade on the NYSE and not by an increase in volume over the remainder of the day. We also find that there is an increase in the time to open for stocks on triple-witching Fridays and a decrease in the time to open for stocks on non-quarterly, option-expiration Fridays.