Few corporate acquisitions occur without a figurative spilling of blood. Studies of several industries have shown that more than half the top executives of acquired companies leave within three years after the takeover. Five years after, that fraction has exceeded three-quarters.Those statistics are hardly surprising. Takeover executives frequently reason that their acquisitions wouldn't have become targets had the managers done their jobs effectively. So the executives bring in their own people to run the acquisitions. Meanwhile, many managers of acquired companies choose to leave even if their jobs are not threatened, because they feel marginalized in the new corporate culture.Do the departures improve the performance of acquired companies? Generally, no. “We have very strong evidence that keeping these people around is one key to better acquisition performance,” says Donald D. Bergh, an associate professor at Pennsylvania State University's Smeal College of Business Administration. However, he believes that which people are kept matters too.In recent research, Bergh confronted two opposing hypotheses favored by representatives of acquiring companies. One asserts that individuals with long tenure offer obvious advantages to their new bosses. They have a greater understanding of the acquired company's culture, mode of operation and day-to-day details.