The number of trades at exchanges run by the CME Group declined by 32% in August compared to a year ago, the company revealed Wednesday.

CME operates the Chicago Mercantile Exchange, the Chicago Board of Trade and the New York Mercantile Exchange.

Combined, an average of 11 million contracts per day were traded at the exchanges for a total of 231 million contracts.

The company said the onset of the credit crunch in August of last year skewed the annual data.

"In August 2007, CME Group recorded its highest monthly volume ever due to the onset of the subprime lending crisis and the ensuing impact on global financial markets," the company said in a press release.

Even with the decline in August volumes, year-to-date trading has averaged 13.6 million contracts per day, up 9% compared to the first eight months of 2007.

In late August, the CME Group closed its $9.4 billion acquisition of Nymex.

By Adam Button and edited by Nancy Girgis