The 2010 U.S. Securities and Exchange Commission rule that requires publicly traded companies to disclose their board diversity policies also requires them to explain their leadership structures to shareholders.

The Institutional Shareholder Services (ISS) Governance Institute says 38 percent of S&P 500 companies had different people filling their CEO and chairman positions in 2010, a 3 percent increase over 2009.

"Separating the chairman and CEO positions is attractive in terms of corporate governance, because it gives the company the option of having an independent lead director," says John McEwan, managing partner of Deloitte's Columbus office. "Whether it's perception or reality, separating the roles gives more room for independent thought and tough questions in the boardroom."

The ISS Governance Institute also found that 65 percent of S&P 500 companies had an independent lead director in 2010, up from 63 percent in 2009.

"It's much more common to separate the CEO and chairman positions today," says attorney Dan Bailey of Bailey Cavalieri. "One outside director is designated the lead director and represents the board vis-à-vis management. It promotes a healthy interchange between directors and with management."

"If an outside director is not the chairman, companies usually name a lead director that has the ability to put items on the agenda and speak for the board. The better practice, though, is to have an outside chair," says attorney John Beavers, a partner at Bricker & Eckler.

Reprinted from the December 2011 issue of Columbus C.E.O. Copyright © Columbus C.E.O.