(Adds analysts' expectations)
Oct 25 (Reuters) - CME Group Inc, the biggest operator of U.S. futures exchanges, reported a plunge in third-quarter profit as investors bought and sold fewer futures and options, but the results beat analysts' expectations by a penny per share.
Earnings, excluding a one-time tax hit, fell to $233.7 million, or 70 cents a share, from $315 million, or 95 cents a share, a year earlier, CME said on Thursday.
Analysts on average had expected a profit of 69 cents a share, according to Thomson Reuters I/B/E/S.
Revenue fell 22 percent to $683 million, missing the Wall Street forecast of $693 million, as trading declined 26 percent.
Expenses, at $287.2 million, were slightly lower than expected, Macquarie Securities analyst Ed Ditmire said in an email.
The excluded tax items were deferred liabilities on CME's stock-index business after it restructured the unit into a joint venture, and on newly acquired technology firm Pivot Inc.
(Reporting by Ann Saphir and Lisa Von Ahn; Editing by Jeffrey Benkoe and Lisa Von Ahn)