Quote from Maverick74:
Go back and look at the ranges from 7/20 to 8/3 in ES. You will notice we had huge ranges on those days. Those data points are dropping off the 20 day roll. Very similar to a 20 day rolling number line. As those wide range days drop off and get replaced with the narrow range August days, it will drag the stat vol down. All the 20 day hist vol is, is the last 20 days of vol annualized. Augen talks about this a lot in his books about how the historical, or stat vol, can be very deceiving.
The implied vol is going into a historically high period, the sept to oct time frame. So forward vol is getting bid up as it should. Based on the data points we have, you will continue to see the hist vol drop as we drop off more higher range days. Of course if we get some really big days this week it will help offset the drop offs.