Ellen. Anderson Cooper. Michael Sam. All three broke barriers by coming out in their respective industries

(comedy, television news and football). Now they're joined by Apple chief executive Tim Cook, who announced in a column in Bloomberg Businessweek that he's "proud to be gay" – and, in the process, became the first Fortune 500 CEO to come out.

Earlier this year, two CEOs of publicly traded smaller firms came out. But until Cook's statement, "don't ask, don't tell" reigned at the highest echelons of corporate America – almost shocking in 2014, given that 91 per cent of Fortune 500 firms prohibit discrimination based on sexual orientation.

As Cook noted, Apple has long taken a corporate stand in support of gay rights and has spoken up against discriminatory laws. But his announcement gives new heft to their commitment.

Cook’s sexuality was long an open secret; as he acknowledged: “For years, I’ve been open with many people about my sexual orientation. Plenty of colleagues at Apple know I’m gay, and it doesn’t seem to make a difference in the way they treat me.”

However, it creates a sort of cognitive dissonance when a company is advocating for equality while its leader remains publicly quiet about his or her own identity.

Walking the talk

Cook’s new openness shows that Apple is walking its talk on diversity – positioning it even more favourably in the never- ending Silicon Valley talent wars. It’s also likely to make him a more effective CEO.

As Sylvia Ann Hewlett and Karen Sumberg reported in Harvard Business Review, being out in the workplace actually has significant advantages. The most notable one is that workers can concentrate on excelling at their jobs and not "managing" their identity. (And remember, there are 29 states in the US where it's still legal to fire someone because they're gay.)

Indeed, even for those who, like Cook, are “out” to colleagues but not to the world at large, the stress of downplaying one’s identity takes its toll.

Research by the Deloitte University Leadership Center for Inclusion showed that 83 per cent of gay employees “covered” at work. That is, even if they were technically out, they still felt the need to minimise their differences by, for instance, not bringing their partner to work functions, or not displaying family photographs at the office.

Out at the top

Cook’s coming out demonstrates powerfully to executives at Apple and elsewhere in the corporate world that covering is no longer required to succeed at the top.

“I consider being gay among the greatest gifts God has given me,” wrote Cook. It has increased his empathy toward others and helped him learn to follow his own path, a key asset in a company that prizes innovation and built its brand on the strength of breakthrough ideas.

“We’ll continue to fight for our values,” he wrote, “and I believe that any CEO of this incredible company, regardless of race, gender, or sexual orientation, would do the same.”

That's probably true, but it means a great deal for Apple, and the many companies that hope to emulate its success, that Cook is willing not just to speak up for equality in general, but also to stand up and be counted. – Copyright Harvard Business Review 2014

Dorie Clark is a marketing strategist and professional speaker who teaches at Duke University's Fuqua School of Business. She is the author of Reinventing You and the forthcoming Stand Out.