Following a shareholder proposal to report on how it pays male and female employees, has added its name to the small but growing list of companies disclosing details about their gender pay gap -- or apparent lack thereof.

The e-commerce giant said Wednesday that a compensation review conducted by an outside labor economist found that among U.S. workers, women earned 99.9 cents for every dollar of their male peers doing similar jobs. "There will naturally be slight fluctuations from year to year, but at Amazon we are committed to keeping compensation fair and equitable," the company said in a statement. Nearly 40 percent of Amazon's employees, but just 24 percent of its managers, are women, according to demographics listed on the company's web site.

The move came several days after the Securities and Exchange Commission declined Amazon's request to exclude the shareholder proposal from its proxy ballot, where investors could cast votes on whether the company should disclose more about its gender pay practices. (Amazon's CEO, Jeff Bezos, is the owner of The Washington Post.)

"I'm very pleased they understand the importance of being transparent and accountable, and I'm glad to see them change their tune," said Natasha Lamb, director of equity research and shareholder engagement for Arjuna Capital, which filed the proposal at Amazon. "We are thrilled to see them step up and say they're committed to gender pay equity." 

With its announcement, Amazon becomes the fourth technology company targeted by Arjuna to disclose its gender pay figure or commit to doing so in the near future. Last month, as part of a broader diversity report, Intel shared that it found no pay gap between U.S. men and women who work at the same job-grade level. Apple CEO Tim Cook disclosed at the company's annual meeting in February that women were paid 99.6 percent of what male peers in similar jobs were paid.

And on Thursday, Expedia said it was committing to disclose its policies and goals for addressing gender pay equity by October, as well as provide information about the percentage gap in salary, bonus and stock compensation between male and female employees.

As a result, Arjuna's Lamb said she withdrew a proposal at all three of those companies, in addition to the one at Amazon, meaning they won't go to a vote at the annual meeting. She said she trusts their data. "We trust that what they report to investors is accurate, just like we trust the financial numbers they’re putting out," says Lamb, who says she has also filed proposals that are pending at eBay, Facebook, Microsoft and Alphabet, the parent company of Google. (Google declined to comment on the proposal, but a spokesperson said in an emailed statement that "our People Analytics team constantly analyzes performance, compensation and promotion to ensure that there is no gender pay gap at Google.")

Another shareholder group, Trillium Asset Management, filed a similar proposal at Citigroup. Citigroup declined to comment beyond what is in its proxy, where it lists  diversity initiatives and says it "remains committed" to them, but encourages investors to vote against the measure because creating the report "would be costly and time-consuming, and in light of our many efforts in this area, would not offer shareholders meaningful additional information."

Why is the pay gap an issue that matters for investors? For one, research has repeatedly shown that more diversity is tied to better performance; in addition, some want companies to get ahead of greater scrutiny that may be coming at the regulatory level. "It's about protecting their brand and attracting women to their companies," Lamb says. "The technology industry lives and dies on innovation, and gender-diverse teams are shown to be a key factor."

Some of the companies targeted said they have been working on analyzing gender pay data long before Arjuna filed its proposals, and that its action wasn't the catalyst for their decision to go public with their numbers.

Still, one consultant who works with companies on diversity issues but requested anonymity because of client relationships said in an email that shareholder actions might be creating a "tipping point" for companies to open up about the pay gap amid other forces. Many tech companies have been increasingly transparent about their diversity data, willing to share often uncomfortable statistics about the low numbers of women in their technology and leadership ranks. Most have sophisticated human resources departments that have long had the capability to carefully analyze pay data. And at a time when the issue has become a hot-button public issue, they're seeing more demands for pay transparency from employees.

Meanwhile, there are new state regulations, such as California's recent Fair Pay Act, which requires that companies be able to prove they pay men and women equally for similar jobs. And earlier this year, President Obama proposed new rules that would require larger companies to report salary data based on race, gender and ethnicity to the Equal Employment Opportunity Commission.

Fatima Goss Graves, senior vice president at the National Women's Law Center, says that while none of these regulations requires public disclosure, the act of preparing the data could prompt companies to take action that would result in good news to share. "Before providing your information to the EEOC, you’re going to take a look and try to correct any problems," she says. "That’s a wonderful time to make the announcement that you don’t have a pay gap. It matters to the public and to consumers. I think in 2016 these are the sorts of questions employees want to know." 

Others could respond competitively to companies who have shared their numbers on their own or promised they would do so. Two years ago, Gap Inc. made headlines for being one of the first companies to publicly say it had audited its outside pay data and pays men and women equally. After CEO Marc Benioff said he was combing through his employees' salaries to look for pay differences, he said he spent $3 million to correct any issues. When SpaceX CEO Elon Musk was recently asked if he would audit employees' pay for any differences, he said he would, according to a report in the Huffington Post.

Whatever the reason behind companies' disclosure of these numbers, corporate governance experts say the idea of having a gender pay proposal on the shareholder ballot is something they'd love to avoid. Nell Minow, vice chair of the governance consulting firm ValueEdge Advisers, says that activists "want to ask a question to which the only good answer is 'we'll fix it.' " With technology companies under increasing pressure to hire and retain more women, "you can't have a better one" than a proposal that targets the pay gap, she says.

Withdrawing a proposal, meanwhile, shouldn't be seen as a sign of defeat. Shareholders rarely get more than a few votes in favor of such proposals, and even if they did, the votes are advisory, meaning companies aren't bound to follow through on the results. "The goal is not necessarily to have a high vote," Lamb says. "The goal is to get the companies to act." 

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