December 2005 futures represented 41% of total trading volume, while November, January 2006, March 2006, May 2006, June 2006 and September 2006 accounted for 10%, 35%, 3%, 7%, 1% and 3% respectively.
On November 30, 2005 the open interest among December 2005, January 2006 - June 2006 and September 2006 contracts was distributed as follows: 18%, 21%, 2%, 13%, 1%, 6%, 15%, 24%.