Updated from 9:14 a.m. EDTThe Chicago Mercantile Exchange ( CME) said Tuesday that earnings jumped 33% in the second quarter as trading in futures continues to boom. But earnings at the nation's largest futures exchange just beat analyst estimates, as the average fee the CME collects on interest rate futures contracts -- the CME's most heavily traded security -- continues to decline. CME earned $109.5 million, or $3.12 a share, compared with $82.2 million, or $2.36 a share in the same quarter last year. Revenue rose 23% to $295.3 million, compared with $239.1 million in the second quarter last year. Analysts, as surveyed by Thomson Financial, were expecting profit of $3.09 per share on revenue of $293.7 million. Average daily volume at the exchange was a record 5.7 million contracts, up 31% from the second quarter last year. Average daily volume of the company's interest rate contract rose to 3.3 million, from 2.6 million in the same quarter last year. Electronic trading on the exchange represented 70% of total volume in the quarter. However, the average fee per contract in the CME's interest rate futures continued to decline in the quarter; this could concern investors after last quarter's performance. Futures are contractual agreements to buy or sell a stock, bond or interest rate product at a specific price. Analysts expect the fees to decrease as volume increases, because the CME offers discounts to traders as their activity at the CME increases. Still, it doesn't seem to be sitting well with Wall Street. In early trading, shares of CME were down $14.49, or 3.1%, to $466.69. Last quarter, the CME, one of the hottest publicly traded exchange stocks to come to market, hit a speed bump when earnings missed analyst estimates. The miss was mainly because of the larger-than-expected increase in trading in interest rate contracts, which is the CME's cheapest futures contract. Wall Street was disappointed that the CME did not show corresponding growth in other, more lucrative futures contracts. This past quarter, the average fee per contract for interest rate products was 47.7 cents, compared with 50.6 cents in the second quarter last year and 49.3 cents in the first quarter of this year. The overall rate per contract was 59 cents, vs. 64.8 cents in the second quarter last year and 63.3 cents in the first quarter of 2006. "CME finished a record quarter with unprecedented volumes across all product lines, particularly in June where volume increased 51 percent," the company said in the release. "During times of geopolitical uncertainty and heightened volatility, the business of managing risk becomes even more important for our users around the globe. We implemented several important technology enhancements last quarter that significantly improved transaction speed and expanded our capacity to handle record volume levels efficiently."