When it comes to building a strong workforce, filling open positions is really only the first step.

While unemployment has remained at a historic low--it stood at 3.8 percent in March--the gender wage gap has barely budged in recent years. Women in 2019 make $0.79 for every dollar men make, up just $0.05 since 2015, according to a recent survey of nearly two million workers conducted by compensation research company PayScale. (Women of color fare even worse--they earn just $0.74 for every dollar a white man makes.)

The good news is, more startups than ever are trying to solve the gender gap in different ways. Here are three that promise to help businesses increase diversity in their ranks.

1. Women 2.0

Founded in 2006, New York City-based Women 2.0 is a media company with a recruitment platform called Lane that helps businesses of all sizes hire women for tech positions. Lane posts job openings from vetted employers and notes whether they have maternity leave policies or the ability to work remotely.

"If it's just a hiring numbers game, and you're not making sure your workplace will support the people you're trying to pull in, you're going to fail," says Women 2.0 CEO Kate Brodock.

About 340 companies wanted to post on Lane's site, but the startup only approved 189, on the basis of how their policies support female employees. Clients range from large companies like Nike to financial startups Alloy and Zeta, and the cost of listing a job opening can vary from $200 for a single job post to $5,000 for a year of unlimited job postings. Female-led companies get a discount. 

2. Fairygodboss

New York City-based Fairygodboss is a platform similar to recruiting portal Glassdoor but only for women. The company lets employers post job listings on the Fairygodboss website, and annual fees start at $35,000. The startup publishes anonymous reviews and insights from a community of more than three million women. Reviews cover topics including salary ranges, the level of flexibility offered, and whether male and female employees receive promotions equally.

"Creating a more diverse workforce is key to creating a more equitable workforce," says Fairygodboss co-founder Georgene Huang.

Since launching in 2015, Fairygodboss has worked with more than 100 companies, including Apple, Salesforce, and Johnson & Johnson. The company reports it has a 90 percent customer renewal rate.

3. Treehouse

Founded in 2010, Portland, Oregon-based Treehouse is an education platform that offers online courses in technological skills like JavaScript, iOS development, and basic website creation. While education is the company's main business model, last year Treehouse launched a program called TalentPath that places aspiring tech workers in apprenticeships at partner companies looking to increase the diversity of their workforce. Since launching, the program has recruited around 150 apprentices, almost all of whom are black or Latinx.

"I [can] use my white male privilege to go to meetings and say, 'This isn't an unsolvable problem, and it's your job to do something about it,'" says Treehouse founder Ryan Carson.

TalentPath recruits talent from local organizations like the Boys & Girls Clubs and Dress for Success, working with individuals typically between the ages of 20 and 40. Apprentices  have been placed at businesses including the email marketing service Mailchimp and business management software company MindBody.