Program Trading In A Falling Market

Look at SPY on March 3rd & 4th, 2010

The high on the 3rd was 112.80
The low on the 4th was 113.10.

That gap wasn’t filled before today.

Look at today’s one-minute intraday chart gradual falling off up until 14:21 EST.

The low was around 112.97 at which point it tried to bounce up but couldn’t hold. The steep sell off got really bad just about the time that false rally crossed back below 112.97 and took out the gap.

It appears there just happened to be a lot of mathematical models around that price point, whether because of the gap or something else. Volume started picking up at 14:00 EST, and then at 14:35 when the support was broken volume really took off in a free fall to the day’s bottom.

There’s no particular spike in volume, just this surge of selling and then buying over the last two hours of the trading day. A lot of stop losses were filled today which probably precipitated the free fall.

Forget the silly rumors of an order error. It's just someone making a joke that a bunch of simple minds believe and repeat until everyone believes it. Today's market action was driven by algorithmic trading and people with day jobs having their risk management strategies triggered by the machines.