Americans are incredibly generous when it comes to opening up their pockets for worthy causes. But a new report finds that philanthropic support wanes when it comes to nonprofits dedicated to addressing breast cancer, childhood malnutrition, female entrepreneurship and domestic violence — in other words, women’s issues.

Americans gave $6.3 billion to nonprofits focused on women and girls in 2016, according to a comprehensive report released Thursday from the Women’s Philanthropy Institute. The Institute identified 45,000 organizations registered in the U.S. that it deemed “dedicated to serving primarily women and girls” or closely-associated causes such as domestic violence, Tessa Skidmore, the project manager for the report, tells CNBC Make It.

That includes organizations such as the Planned Parenthood Federation of America, the Susan G. Komen Breast Cancer Foundation, the National Women’s Law Center and YWCA chapters around the country.

And while $6.3 billion may sound like a substantial level of funds, it actually only represents about 1.6% of the total charitable giving Americans put forward in 2016. To put that in perspective, Americans gave a total of $396.5 billion that year, with the biggest chunk, $123.8 billion, earmarked toward religious organizations.

“There is a lack of investment in women and girls in this country,” says Teresa Younger, president and CEO of the Ms. Foundation for Women. “The Women’s March and some of these other movements are heightening a conversation, but I’m not sure how that’s trickling down to the small grassroots orgs that are doing the work within their communities.”

Younger, who tells CNBC Make It that she lives this reality everyday, notes there needs to be “intentional support” of the organizations that have been put in place to help lift up, empower and build the power of women and girls. And not just in the health-care sector, which WPI found received the biggest chunk of the total funding directed toward women and girls.

Yet even though so few dollars are going to women and girls, nonprofits are still able to have significant impact, Younger says. About 71% of nonprofits dedicated to women and girls have budgets of less than $50,000 — and that includes staff wages and benefits. The report speculates this may be due to a heavy reliance on volunteers, but Skidmore says more research is needed.

“In most cases, usually women are running very efficient organizations and paying themselves and relying on the kindness of their communities to allow them to do the work that needs to be done,” Younger says.

Where to donate to support women and girls

If you’re looking to boost your donations to women’s nonprofits, Younger says a good starting place is to look up women’s foundations or funds in your area. For example, the New York Women’s Foundation, or the Women’s Fund of Central Ohio or the Arizona-based Fresh Start Women’s Foundation.

“Those organizations are supporting their grassroots groups and supporting the women and girls in the community,” Younger says. Plus, by using a women’s foundation, you can make one donation, and you don’t have to vet several individual organizations.

If you are interested in giving locally, pay attention to the mission statement of the organization and make sure it’s really specific. “If they say they’re helping ‘youth’ or ‘community,’ broadly, then they’re not being specific about what they’re doing to help women and girls,” Younger says. “And if they don’t say it, then they aren’t doing it.”

“We need to start looking at what strategies can sustain nonprofits over time, what supports they need to have, and how we are building the power of women and girls in this country,” Younger says.