Arjuna Capital managing partner Natasha Lamb has convinced 21 companies to commit to analyzing and closing their gender pay gaps. These include major players in tech (Apple, Intel, Microsoft), finance (J.P. Morgan Chase, Bank of America, Mastercard), and retail (Amazon, Nike, Starbucks). In honor of Equal Pay Day 2018, Fortune sat down with the activist investor to talk about how—and why—she engages with companies on the issue of pay equity. The interview below has been edited and condensed for clarity.
Fortune: Bloomberg recently called you one of the 50 most influential people in business for your work on equal pay. Can you please explain what you do?
Natasha Lamb: Arjuna Capital is a wealth management firm focused on sustainable and impact investing. We look to widen the lens on how we evaluate our investments, taking into account environmental, social and governance criteria and looking beyond traditional methods of analysis to incorporate the sustainability factors. So when it comes to the pay gap, we’re asking companies to close the gender pay gap and commit to keeping it closed.