Quote from cstfx:
As to why one would trade the mini? Volume, baby! You can get the daily volume figures off the CME website, but as an example, on Weds past, e-mini total volume was 1.6M contracts whereas the big contract only did 32K.
I always assumed that emini contracts were being offset by positions in the regular S&P. In other words, a 'big' trader would buy the S&P and offset it by sellng ES to smaller traders. Don't know why I thought this.
Coincidental maybe: 32,000 S&P contracts is equal to 1.6 million ES contracts.