Corporate Directors Pressured to Serve on Fewer Boards

Investors are increasingly pressuring corporate directors to limit how many boards they sit on as the job becomes more demanding.

Top institutional investors such as Vanguard Group and BlackRock Inc. have updated their policies for voting in board elections to discourage what they see as too many directorships at once. Companies have also been adopting their own policies restricting how many other board seats their directors can hold.

Most of the roughly 21,000 directors at companies in the Russell 3000 index sit on just one board each, data from Institutional Shareholder Services Inc. show. But almost 6,000 of these directors ...