You might find a answer here.
http://www.turtletrader.com/borish-baldwin.html
Peter Borish: Tom, when you are down on the floor and you see all sorts of price activity taking place, for example tomorrow we know unemployment figures are coming out and the only thing we know for certain is there is going to be volatility after the number. Compare how you step up and provide that liquidity in the marketplace, somebody like me vs. what happens for the downstairs. Who makes the first more after a number comes out? Is it locals or somebody upstairs putting in an order to trade?
Tom Baldwin: With your example where the number is so important, it is usually a combination of both. Everybody knows what the effect of the number is going to be. So if it is way out of line, the people in the pit understand the market is going to go is the direction that it is out of line. The upstairs orders also come in at the same time. The object is to move the market as far as you can to a point where you buy or sell at that level, so there can be a two way trade. Nobody want's to be the face plate on the train. There is no point in it.
Peter Borish: (Sarcastically) But, it opens @ 97. It says in the daily range that it's from 97 to 98, how come after the number came out @ 97.04, I can't filled @ 97.06? I want to buy a lot there!
Tom Baldwin: The reason you can't is that is really not the market. At 7:29 am before the number comes out the market is at 'x' and then when the number comes out and its out of line, the actual market has a gap between where it eventually goes to and where it starts. And in between there is really nothing there because the market is now here. And most people are not accustomed to that jump and they are not aware that there is really nothing to trade there, unless it is by luck. i.e. there was resting order that happened to be there, doesn't happen often. So you would never get filled at those prices. It would be very easy if when the number came out and you said gee that's way out of line and it's really bullish and I want to be long 1000 bonds, well the rest of the world is not stupid either and they see its out of line so they decide not to sell now. When it rallies a point then I'm going to sell it. Because that is where the market should go to based on that number. It's like saying I wish I could buy 1000 bonds a point below market, but it's not the market.