Hmmm.. these are just guesses on my part but the ES is very closely tied to the performance of its pit-traded big brother and the pit traded S&P 500 is largely made up of the giant computerized program trades (they say program trading accounts for more than 63% of all trade volume there).
The ES is clearly the liquidity beast of the online futures game, there is no doubt about it so yes, I suppose in theory it could perhaps be easier to manipulate the far less liquid online markets of the YM and the ER2 compared to the ES. However, the far lower liquidity levels of these other online futures markets probably precludes the largest traders from taking much of an interest at this stage as they cannot easily float anywhere near the size they need to meet their profit expectations.
As was already noted, a 1,000 contract trade on the YM would not only move the market, it is simply seldom if ever seen. Bigger traders who may occasionally dabble in the smaller electronic markets beyond the ES most often break their large trades down to disguise them and seldom take them all in one fell swoop anyway. They don't want other players piling on at their level, they are more dependent upon the mass horde of retail traders jumping in more toward the end of the move so it is then easy for them to exit for a tidy profit. They don't want to give away their intent from the very outset.
I also think that with the more limited liquidity of the YM, a 100 lot contract size or greater would suffer a good deal of slippage in getting the whole thing placed in addition to alerting everyone else to the point of your participation and the the possible strength of your trade.
I would certainly love to hear other viewpoints on this as I find the idea somewhat intriguing.
Happy Trading
