Now here’s some surprising news.

According to a recent Mercer Consulting Group study, the majority of large trans-Atlantic mergers completed between 1994 and 1999 — 82 of 152 deals studied –outperformed industry market value benchmarks. Over the years, most M&A studies have concluded that these sorts of U.S/European deals typically don’t work out.

But Mercer’s study reveals that, during the 1990s, the number of trans-Atlantic deals and the size of the transactions averaged 30 percent annual growth. European-led deals outnumbered American-led deals by more than 50 percent.

“Success” was calculated as the market value growth of the acquirer — from one month pre-announcement to 24 months post-announcement — as compared to the market value growth of its corresponding industry index over the same time period.

So why did these trans-Atlantic mergers work? Mercer said that in interviews with senior executives who successfully completed these kinds of deals, a number of them pointed to post-merger integration as the key to success.

“Most trans-Atlantic deals are expected to face greater regulatory and cultural barriers,” said Mike Lovdal, a Mercer Management Consulting vice president who directed the research effort, in a press release. “That leads to a more careful integration process.”

Lovdal added that corporate governance structures, shareholder interests, and regulatory philosophies affecting many trans-Atlantic deals “form a natural screen for poorly conceived deals to get weeded out.”

Mercer said it looked at other possible drivers of performance but found little or no bearing on M&A performance resulting from the premium paid, pre-deal performance of the acquirer, relative size of the parties involved, or strategic intent.

“Most trans-Atlantic deals are driven by expectations of revenue growth, but this is much more difficult to achieve than cost savings,” said Lovdal, adding that “post-merger integration in successful deals has been focused on revenue-related issues such as customer communication, sales channels, and brands.”