When NYSE went down today at 3:50 I would have expected there to be a lot of volume shifted over to ECN's from day traders wanting to get out of their positions. But this was not the case. I didn't see much additional ECN activity at all. And was stuck in lots of positions. So conclusion is that in any 10 minute period there is very little day trader open interest (traders who have a trade open). I noticed on my screens that day trader open interest dropped off big time about 2 1/2 years ago. I think before all the program trading there was day trader open interst created by institutions and trade desks looking to work larger orders. But now they just route these orders via program trading in 300 share lots which is all automated. Just a theory.