/ Updated 
By Noel Gutierrez-Morfin
Thomas M. Barwick / Getty Images

A record number of companies are making LGBTQ-inclusivity part their workplace policies, with 517 companies receiving a perfect score of 100 on the Human Rights Campaign's Corporate Equality Index.

The HRC's Corporate Equality Index (CEI) began in 2002 and measured companies based on four core attributes: basic nondiscrimination protections for LGBTQ employees (even though state-mandated protections were slim at the time); employee benefits, such as domestic partner benefits; internal or external training; and respectful external engagement with the LGBTQ community. Though the CEI has evolved over time, these key principles have continue to inform their evaluations of companies and businesses.

Since the first edition of the CEI, exponential progress has been made. According to a press statement, in 2002, when the CEI first started, only 3 percent of Fortune 500 companies had nondiscrimination policies that included gender identity. Now, 82 percent of companies have implemented these protections.

“Even in the face of relentless attempts to undermine equality, America’s leading companies and law firms remain steadfast and committed to supporting and defending the rights and dignity of LGBTQ people,” HRC President Chad Griffin said in the press statement.

“The unprecedented expansion of inclusive workplaces across the country and around the globe not only reflects our progress, it helps drive it. As we enter a new chapter in our fight for equality, support from the business community will be more critical than ever to protect our historic advancements over the last decade and to continue to push equality forward for workers, customers, and families around the world.”

RELATED: Best Practices for a Transgender-Inclusive Workplace

The CEI also noted that nearly 86 percent of all businesses included in the index have training and workshops on gender identity in the workplace, and 73 percent offer trans-inclusive health care coverage.

"One of the biggest influencers for this progress is competition. When early adopters--the first airline, the first bank, the first manufacturing company--adopt these policies or benefits for LGBT employees, other companies, their peers, want to catch up to them," Deena Fidas, director of HRC's Workplace Equality Program, told NBC OUT.

"There's also the power of the human story. We have LGBT people able to bring their full selves to work, and when company leaders have these employees, they're thinking about their valued colleague, and not an abstract concept of human rights. It becomes about valuing and retaining talented employees," Fidas added.

Apple was one company that received a perfect 100 score from the Human Rights Campaign's Corporate Equality Index for LGBT-inclusiveness.Eric Thayer / Getty Images

Companies with a perfect 100 on the CEI include Apple, General Electric and Ford Motors. The law firm McDermott Will & Emery also received a perfect score.

“It fills me with pride to know that McDermott has once again received top marks on the Corporate Equality Index,” Michael Weaver, the partner in charge of LGBTQ diversity and inclusion at the firm wrote in a statement sent to NBC Out. “For us it’s not just about achieving a perfect sore but rather it’s about proving –- day in and day out –- that the Firm is truly committed to nurturing an inclusive culture that celebrates diversity.”

According to Fidas, there's a very real, financial reason for businesses and companies to make themselves more LGBTQ-inclusive.

"We've studied 'the cost of the closet,' or the cost of losing people to unwelcome workplaces and the decisions that push LGBT workers to leave, or the cost of having your employees face an unwelcoming environment. Employee engagement can decrease by 30 percent. A key part of avoiding this engagement decrease and turnover cost is investing in LGBT-inclusive policies, protections and practices. Domestic partner benefits only constitute a 1 percent spending increase for companies, so the cost of losing talented employees to rival companies definitely would be more than the initial investment."

Fidas also noted the LGBTQ community has approximately $900 billion in spending power, so from a standpoint of attracting consumers who are a part of that community, being LGBTQ-inclusive just makes business sense, she added.

Follow NBC OUT on Twitter, Facebook and Instagram.