The turnover rate of chief executives at the world's wealthiest companies jumped 10 percent in 2007, according to a study by New York-based public relations firm Weber Shandwick.

Last year, 81 CEOs at the world's top 500 companies by income left their jobs, including 27 at North American-based businesses alone, the study found. At 16.2 percent, the rate of CEO outplacement is approaching a 16.4 percent global high set three years ago.

Over half of North American CEOs left their jobs at the end of last year. The sharpest level of turnover was in the telecommunications and financial sectors.

"Although many CEOs leave for ordinary reasons such as retirement and succession planning, an increasing number also leave involuntarily," Leslie Gaines-Ross, a Weber Shandwick spokesperson, said in a statement. "Just as CEOs receive most of the credit when things go right, they are expected to accept the majority of the blame when things go wrong."