In “Chairing the Board: The Case for Independent Leadership in Corporate North America,” the authors propose that all companies with a current CEO-chairman leader split the roles upon the incumbent’s departure, or explain to shareholders why they chose not to.

The movement to split the two main company leadership roles is growing, with 37 percent of S&P 500 companies currently having separate chairmen and CEOs, compared to 22 percent in 2002. International companies, particularly those in Germany and the Netherlands where a split is mandatory, have roundly adopted such a system.

The Chairmen’s Forum, led by retired GM vice chairman Harry Pearce, is designed to promote “deeper understanding of independent board leadership practices and [reach] out to the wider market on effective practices of board chairmanship.” The group was founded early in 2008 and will meet next on July 31.