The Wellesley Centers for Women issued a report in late October about the relationship of the percentage of women on boards of directors and corporate governance practices. The WCW report finds that there is a critical mass of women in the boardroom for the company to benefit significantly from their perspectives, interpersonal skills and understanding of certain issues. Companies that have at least 3 women on the board of directors tend to benefit in the area of governance. If only one or two women are on the board, those one or two women may simply be viewed as tokens and those women may not be able to influence the discussion in the ways that 3 or more women can.
Interestingly, Norway seems to be way ahead of many other countries in having women on boards of directors, but Norway got there through legislation. Since 1985, Norway has required that public companies have a board comprised of at least 40% (depending on board size) women. Now, women hold about 44% of the public company board seats in Norway.
Legislation seems to be an extreme solution, but the Wellesley report is probably right about there being a certain critical mass. I serve on a college's board of trustees and when I joined the board, it was the first time one of my fellow trustees could say, to his delight, "Ladies and gentlemen . . . "