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.
Here's what companies can do to help close the gender pay gap 
Shareholder resolutions
Chances are, if you invest in a fund that bills itself as gender-focused, you will count on it to make shareholder votes that keep those issues in mind.
But Morningstar did an analysis of three funds focused on this area and found that that is not always the case.
The three funds Morningstar reviewed include Glenmede Women in Leadership U.S. Equity Portfolio, Pax Ellevate Global Women's Leadership Fund and SPDR SSGA Gender Diversity ETF.
Those three funds voted 47 times on 32 resolutions related to gender from 2016 to 2018.
But when it comes to pay equity disclosure resolutions, for example, their support was not unanimous. The Glenmede fund voted for these resolutions eight times, while the Pax Ellevate fund affirmed its support 12 times.
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State Street Global Advisors' fund, however, voted against pay equity disclosure resolutions four times and abstained from voting once. The fund had no votes on record in favor of pay equity disclosure resolutions during that time period.
Much of State Street's voting record can be attributed to a different approach it takes to advocacy on these issues, according to the firm. That includes more direct engagement with companies instead of emphasizing shareholder resolutions, where the proposals can be too prescriptive or may not approach gender issues in the way in which the firm would prefer.
In most cases where State Street voted against or abstained from voting, they voiced their concerns on these issues directly with the companies.
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.
