Women matter far more than the business world has traditionally acknowledged. Studies now suggest that companies perform better with women leaders. The ranks of women near the top of businesses are growing, but slowly. According to a recent BloombergBusinessWeek report, close to 10% of S&P 500 companies -- 47, to be exact -- have no women on their board of directors. That's a stupid risk to their performance and prosperity.

The evidence
My colleague Alyce Lomax cited a 2010 McKinsey study, which found that companies with women on their boards outperformed those without by 41% in terms of equity, and 56% in operating results.

Women and men often think in different ways, and in general have different dispositions. Per a recent Vanguard study of people earning between $30,000 and $75,000, a significantly greater percentage of women than men made 401(k) contributions. In this case, at least, women are clearly making the smarter choice.

Half-baked arguments
When asked why they don't have women at the top, some companies explain that their industries harbor too few women with the required expertise, shrinking the potential pool of candidates. But financial journalist Terry Savage scoffs at that argument, noting that she sat on the board of an oil company for six years:

The fact is that more than half the employees of that hugely industrial corporation were women … I did not have to be an expert on drilling to be on that board. There is always something that a woman can contribute.

Consider Titanium Metals (NYSE: TIE), the world's largest titanium supplier. In 2003, it settled a sexual harassment lawsuit for $217,500. Although the company admitted no wrongdoing, I question whether the company's lack of women on its board, in top management, and among its highest-paid workers conveys a message that it doesn't value women's contributions. At the very least, putting women in positions of power would make the company seem less like a boys' club.

Facing challenges
Many of the 47 companies with all-male boards might benefit from additional perspectives as they face their respective challenges. MEMC Electronic Materials (NYSE: WFR), for example, is pinning a lot of expectations on selling chips to solar energy companies such as JA Solar (Nasdaq: JASO), with which it has a contract through at least 2012. However, its recent negative free cash flow has left investors worried.

Meanwhile, several companies with no women at the top now report sizable insider sales. That's not necessarily a bad thing; many executives get paid largely in stock, and do occasionally sell some. But MetroPCS and NetApp (Nasdaq: NTAP) have seen 114 and 20 insider sales, respectively, in the past six months, representing 15% and 21% of their insiders' respective stock holdings. If these companies' boards aren't inspiring insiders to hang on to shares, perhaps they need some new perspectives.

The paucity of women at the top of organizations is also puzzling, considering that so many companies either already serve many women, or are trying to attract more as customers. Urban Outfitters' stores tend to be full of female shoppers. The company's sales have not been growing as briskly as rival apparel retailers such as Buckle. More women executives might help steer Urban Outfitters in a more profitable direction.

Even companies with one or two women on their boards deserve some questioning. Sirius XM Radio (Nasdaq: SIRI) has two women out of 13 directors. That's much better than many companies, but it's still low for a company clearly seeking to draw a female audience with programming from Oprah, Martha Stewart, Rosie O'Donnell, and more. Having an even more diverse board could help it reach and engage even more women listeners. 

Lowe's (NYSE: LOW), with one woman on a board of 12 people, has been actively trying to draw more women by revamping its displays and offering more private-label wares. Home improvement chains such as Lowe's have long catered mostly to men, but it makes sense to attract more dollars by appealing to women, since they do manage many households and have a say in many home-related purchases. Having more than a lone female voice on its board could help Lowe's succeed even more in this realm.

As you seek great companies for your portfolio, keep an eye on the diversity of their management. Companies with more women on board often boast better profitability and happier shareholders.

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