Post on Carl Futia's Site

Note the huge discrepancy between TICK and price in the last 10 minutes. Here's a chart: http://tinyurl.com/29l66em SPX is in green. This happens when a few stocks that comprise a large part of the index are sold heavily. This is quite easy to do, and drives fear into the market, brings the narrower indices down. This will increase volatility, lots of people will buy Puts, which will be shorted. You could also look at the difference between the RUT and SPX in the last 5 minutes, and it would show you the same thing. Note the ending dip in the SPX and how you don't see it in the RUT? Options Opex is next Friday.