As a past market maker and backer of market makers, I echo ajacobson and newwurldmn adding that there are many firms that have algos trading stocks and some options near the close that will create additional volatility near the close.
We take a snapshot of markets 14-minutes before the close. We subjectively picked that time as most representative of the true markets before the EOD shenanigans start.
Here's a picture of this past Friday SPY falling right before the close.![]()
I am suggesting that representative options markets are better reflected well before the close. Many firms trade large size on the close. One of our clients trades like this. It makes it very difficult to hedge an options trade when the volume is so great in the underlying. There are methods for notification of imbalances on the close and that information sometimes makes the options markets look odd.Are you suggesting this might have been EOD shenanigans? Volume is usually highest in the last 10 minutes though, right? Are prices on the greatest volume the most representative?