Backdating companies share board members: Study

Of 120 companies under investigation for backdating stock options, 42.5% have directors who sit on more than one board within the companies implicated in scandal, according to a report released Thursday by The Corporate Library, a Portland, Maine-based corporate governance research firm.

The findings suggest, but do not conclude, that the practice of backdating stock options spread by word of mouth among directors, according to the study. The "theories behind social networking would support such a theory very strongly," the report states.

"The frequency of links via a shared board member with the group of 'scandal' companies is much higher than can be found among randomly selected groups of U.S. public company boards," according to the report.