A leading U.S. executive search firm has found that Japan's corporate boards have a smaller number of external directors than any other nation.

Officials of Korn/Ferry International said their findings are not meant to endorse a particular style of corporate management. They cited as an example Toyota Motor Corp., which is globally successful yet hires all of its board members from within the firm.

But a growing emphasis by boards worldwide to take on external directors presents a new business opportunity for Korn/Ferry, which, like other top-end executive search firms, is facing a tough market environment, said Korn/Ferry Chairman and Chief Executive Officer Paul C. Reilly, who visited Tokyo last week.