Amazon.com Inc. has adopted a policy to include a "slate of diverse candidates," including women and minority candidates in director nominations, the Seattle-based e-commerce giant said in a May 14 filing to the SEC.

The company revised its board of directors guidelines on "significant corporate governance issues" to include a clause about creating a board with a diversity of experience and perspectives, "including diversity with respect to race, gender, geography, and areas of expertise."

Amazon said the revision of the policy "formalizes a practice already in place."

The e-commerce giant's 10-member board currently includes three female directors.

Amazon's SEC filing updating its policy follows calls from investment groups led by CtW Investment Group and SEIU Pension Plans Master Trust, which have been pushing the board to adopt the policy.

CtW first put forward the proposal in a Nov. 30, 2017, letter to Amazon Chairman and CEO Jeff Bezos, suggesting that the company adopt a National Football League-style "Rooney Rule," which would require the company to include qualified women and minority candidates in its board search.

Amazon filed an initial proxy statement April 18, urging its shareholders to vote against the proposal, saying it had already sought out candidates with a "diversity of experience and perspectives."

The company said at the time that its processes for director nominations "involve complex considerations that are designed to advance the long-term interests of shareholders." It added that the adoption of the policy requested by CtW would not be an effective use of the company's time and resources.

CtW and SEIU subsequently wrote to shareholders April 27, pushing back against Amazon's statement. The investor group argued that embracing diversity will benefit companies by providing greater access to talent and improving decision-making by reducing psychological biases.

The group noted that the Rooney Rule has been implemented in the director search process of companies such as Microsoft Corp. and Costco Wholesale Corp.

Most recently, Amazon Vice President of Public Policy Brian Huseman wrote to the Congressional Black Caucus, saying the company reached the decision after listening to feedback from the organization, Amazon's shareholders, employees and other stakeholders, technology newswire Recode first reported May 14.