This quarter's slowdown has been most pronounced in Europe, where takeovers accounted for about $92 billion, or 21 percent, of global activity, the continent's lowest share since 2010. The Americas accounted for $248 billion of transactions, and there were $104.5 billion in the Asia-Pacific region.

The deals that are getting done are notable for cross-border cooperation. More than $720 billion in takeovers this year involve companies in more than one country, the highest share in five years, data compiled by Bloomberg show.

That includes Cnooc's purchase of Canada's Nexen and Belgium-based Anheuser-Busch Inbev NV's $20.1 billion buyout of the shares of Mexico's Grupo Modelo SAB that it didn't already own. EADS, based in Toulouse, France, and London-based BAE said this month they are in talks on a transaction that would potentially create the largest European aerospace and defense company with a combined market capitalization of more than $40 billion.

“What's remarkable about this year is the size of the cross-border transactions we're seeing,” said Michael Carr, head of Americas M&A at Goldman Sachs Group Inc. “They're notable in a market that's characterized by caution.”

Goldman Sachs is the busiest merger adviser so far in 2012, working on more than $375 billion of transactions, ahead of Morgan Stanley and JPMorgan Chase & Co. Goldman Sachs took first place last year in Bloomberg's ranking after Morgan Stanley led in the previous two years.

Europe's Troubles

There are fewer deals to fight over this year, partly because of Europe's extended sovereign-debt woes. The crisis has forced leaders to implement aid packages in Greece, Ireland and Portugal to help preserve the 17-nation euro zone, with the euro area bound for recession. That put a damper on the merger market, said Adrian Mee, London-based head of international M&A at Bank of America Corp.

“There is still a fair bit of concern about investing in Europe in general, and southern Europe in particular,” Mee said. “There needs to be a sustained period of confidence in the macroeconomic outlook for the pace of deals to pick up significantly.”

China's economy also has shown signs of deterioration as manufacturing slows, increasing the chance that the country may fail to surpass its growth target for the first time since 1998.

Still, Asian buyers struck $133.9 billion, or about a third, of this quarter's deals. Besides Cnooc-Nexen, the biggest proposed transactions include Thai billionaire Charoen Sirivadhanabhakdi's S$9 billion ($7.3 billion) bid for a 70 percent stake in Fraser and Neave Ltd. and Tokyo-based Dentsu Inc.'s 3.16 billion pound ($5.14 billion) purchase of British advertising firm Aegis Group Plc.

“Asia is long capital, assets globally are cheaper, the parties out here have balance sheets that are sound and they are in a position to pursue international assets,” said Matthew Hanning, UBS AG's head of investment banking for the Asia-Pacific region.

Asia's quest for raw materials to fuel an industrial expansion has bolstered deals involving natural resources and energy companies. Sales of such companies account for about 21 percent of the merger market this year, almost twice their share during the first decade of the 21st century.

Natural Resources

“This is a trend that will continue for a significant period of time,” said Nigel Robinson, London-based head of energy and natural resources at Deutsche Bank AG.

Private-equity firms are playing a bigger role this year, selling companies they bought during the buyout boom of 2006 and 2007, and investing in new leveraged buyouts, said Anthony Armstrong, co-head of Americas M&A at Credit Suisse Group AG.

LBOs increased to $39 billion this quarter, the most in more than a year and about 9 percent of all merger activity. Carlyle Group led the way with $15 billion of transactions, including $4.9 billion for a DuPont Co. auto-paint unit and $3.5 billion for a division of United Technologies Corp.

“Sponsors have been quiet for a couple of years, but they're back,” said Armstrong, who is based in San Francisco.

Bednar, of Perella Weinberg, predicted that merger activity will continue to track this year's $2 trillion pace, and that the record $4 trillion of deals struck in 2007 during the height of the leveraged-buyout boom may stand for some time.

“It's not a small market — it continues to be a very large market,” he said. “But I'm not sure we're going to see the amplitude of peaks and troughs as high as they've been historically. It'll be much more of a steady state.”

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