As a means of thwarting shareholder proposals seeking to have the offices of chairman of the board and chief executive officer held by different individuals, public companies are increasingly appointing lead directors. A lead director represents the members of the board of directors and does not have ties to the public company. Lead directors typically run executive sessions of the board of directors at which members of company management are not present. Lead directors also often hold veto power over board of directors' agendas, help settle disputes between the company and key shareholders, challenge executives on business risk exposure and conduct chief executive officer performance reviews. According to data compiled by a leading national executive search firm, the number of lead directors at S&P 500 companies rose to 247 in 2011 from 165 in 2006.