NEW YORK (Bloomberg) ? Marsh & McLennan Cos., the world's largest insurance brokerage, will begin requiring board directors and senior executives to own minimum amounts of company stock.

Directors must hold at least $100,000 of common stock or other equity within three years of joining the board, the New York-based company said in a statement today. The minimum for senior executives is a multiple of their base salary.

The rules are part of a series of new corporate governance guidelines. Directors should not serve on the boards of more than four other public companies and must offer to resign if their job or personal circumstances change, the company said.

Shares of Marsh rose 63 cents, or 2.2 percent, to $28.91 at 11:42 a.m. in New York Stock Exchange composite trading. The stock has dropped nine percent this year, underperforming the 4.6 percent advance in the KBW Insurance Index.