Boosted by America Online_s mega-offer for Time Warner, corporate merger activity is off to a fast start this year in dollar terms.

Yet deal activity overall is running at the slowest pace since 1995. Through Tuesday, 2,270 mergers involving U.S. companies have been announced this year with a dollar value of $537 billion, according to Thomson Financial Securities Data. The dollar total is already the strongest for any first quarter and is the second-biggest overall, after the $677 billion of deals announced in the second quarter of 1998. But the number of deals is the lowest for any quarter since the second quarter of 1995. Since peaking at 3,409 announced deals in the third quarter of 1998, the quarterly totals have declined fairly steadily. But if the dwindling number of obvious bargains means potential buyers are finding less to buy, the deals are bigger than ever. The average size of deals announced in the first quarter is $236 million, or $156 million not including AOL-Time Warner. That compares with an average size of $155 million for all of 1999 and $134 million in 1998. As in the case of AOL-Time Warner, most mergers are stock-for-stock transactions. Deals using cash as payment have accounted for only 24 percent of the value of deals announced this quarter. By contrast, 10 years ago cash deals and stock deals were split nearly evenly.