Nancy Reichman, a member of Colorado's Pay Equity Commission joins in a rally in downtown Denver, CO. Colorado citizens and activists from 9to5, National Association of Working Women and Coloradans for Fair Pay gathered on the steps of the Colorado State Capitol, to mark national Equal Pay Day. Craig F. Walker | Denver Post | Getty Images

Women earn just about 80 cents for every dollar that men make, and that difference can add up big over time. A women who starts her career today will miss out on $406,760 in earnings over 40 years, according to new estimates from the National Women's Law Center. With more public attention to this issue — and with April 2 marking Equal Pay Day — gender and diversity funds have emerged to help investors identify companies that are paying attention to these concerns. The universe of funds operating in this area is relatively small. New research from Morningstar identifies a total of 15 equity mutual funds and exchange traded funds that it categorizes as gender and diversity sustainable investments. But just investing in those funds does not always mean you're directly moving the needle when it comes to closing the gender pay gap. Morningstar's research identifies two key reasons why.

Shareholder resolutions

Mixed results

Just because an issue like gender pay equity comes up as a proxy vote does not necessarily mean it will be successful. In June 2017, a resolution requested that Mastercard prepare a report by November of that year on how the company planned to address the gender pay gap. But because it only had 7.8 percent support, it did not go through. In contrast, a separate gender pay equity proposal at eBay Inc. in April 2016 received much more broad support, with 51.23 percent, according to Morningstar's report.