Gender equality isn't nabbing mainstream media headlines like other SRI issues such as climate change and executive pay, but its shareholder advocacy efforts are going strong.

During the 2010 proxy season, Pax World Management LLC, investment advisor to Pax World Funds and a leader in sustainable investing, withheld votes from 74 board slates because those companies didn't nominate any women directors.

Feedback to its vote withholding and follow-up suggestions regarding gender diversity is getting a little stronger each year, says Joe Keefe, Pax World president and CEO.

Pax World also sent letters this summer to the CEOs of 82 companies held in its Global Women's Equality Fund-the only mutual fund in the U.S. that focuses on investing in companies that promote gender equality and women's empowerment-urging them to embrace the Women's Empowerment Principles (WEP).

So far, nearly 40 companies worldwide have agreed to support these principles, which outline how to empower women in the workplace, market and community. WEP is a joint initiative of the United Nations Development Fund for Women (UNIFEM) and the United Nations Global Compact. They're based on the Calvert Women's Principles initially launched in 2004 by Calvert Group Ltd. and UNIFEM.

Another recent development on the gender equality front: Entertainment company Netflix Inc. amended its director selection language and then appointed its first female director to its board following a resolution jointly filed by Calvert Asset Management Company and the Connecticut Retirement Plans and Trust Funds.

"Gender equality and women's empowerment have to become core principles of ESG (environmental, social and governance). Gender inequality is probably the No. 1 impediment to sustainable development," says Keefe.

Additionally, many studies show the status of women is an excellent clue to a company's growth potential, he says. For example, a 2007 Catalyst study found that Fortune 500 companies with the highest representation of women on their boards outperformed those with the lowest representation in return on equity (by 53%) and return on invested capital (by 66%). Those with the greatest percentage of women on their top management teams also significantly outperformed those with the least, found a 2004 Catalyst study.

"When women are at the table, the discussion is richer, the decision-making process is better, and the organization is stronger," says Keefe.

Leadership diversity isn't the only gender-related criteria that interests Pax World. It also looks at companies' career development, education and training programs; hiring and promotion policies; work-life balance initiatives; nondiscrimination and violence policies; use of women suppliers; and portrayal of women in advertising and marketing material.