True corporate diversity can’t be achieved unless it’s reflected at the top. And given the persistent dearth of black professionals in power roles at major companies, corporate America has a long way to go.

There’s growing awareness of the need for diversity at all levels of the workplace – not just because giving equal opportunities to all is the right thing to do, but because it helps companies better innovate and compete as US demographics and consumer habits change. Yet numerous studies show the number of black professionals on boards and in C-suite roles range from not great to dismal.

Companies are not required to disclose the race and ethnicity of their C-suites and boards, so the statistics that do exist are often collected by hand or extrapolated from surveys.

Here’s a sampling of what we know from a variety of sources.

Black professionals overall: Black professionals in 2018 held just 3.3% of all executive or senior leadership roles, which are defined as within two reporting levels of the CEO, according to the US Equal Employment Opportunity Commission.

Black CEOs: Among Fortune 500 companies, less than 1% of CEOs are black. Today there are only 4, down from a high of 6 in 2012, according to Fortune. And over the past two decades, there have only been 17 black CEOs in total. Of those, only one has been a woman – Ursula Burns, who ran Xerox from 2009 to 2016.

Black executives in C-suite and other high power roles: Those most often promoted to CEO or named to corporate boards usually have held one or more specific titles – CEO, chief financial officer and regional or division president in charge of business units that deliver significant profits to the company overall.

But among Fortune 100 companies this year, black professionals account for just 3% of CEOs, 1% of CFOs and 3% of profit leaders like division presidents, according to calculthe Stanford Corporate Governance Research Initiative. While black professionals account for a comparatively high percentage of chief human resource officers (13%) and chief administration executives (43%), the chances of being promoted from there to a CEO or board role are low.

Black executives in the boardroom: Black Enterprise’s 2019 Power in the Boardroom report found that among S&P 500 companies, there were 322 black corporate directors at 307 companies. Of those, 21 were chairmen and lead directors. But the report also found that more than a third of S&P 500 companies did not have any black board members whatsoever.

Why the persistent dearth?

There are several reasons why black professionals are not better represented in the halls of corporate power to reflect the roughly 13% of the US population they comprise.

A critical one is that corporate leaders aren’t doing enough to develop a pipeline of black talent to promote into the C-suite and to be named to boards, said Cari Dominguez, former chair of the EEOC and a member of the National Association of Corporate Directors. “I see companies asking for a diverse slate of candidates – but not saying [what percent] should be made up of people of color.”

The culture of promotion can also exclude qualified black candidates, who may not be part of the social networks that board members and CEOs often use to vet a candidate.

And since boards are typically risk-averse, they tend to go for the same types of candidates, such as active or retired CEOs and executives who have already served on boards. Since there are so few black executives in those categories to begin with, the same black professionals tend to be chosen again and again, noted Dominguez, who is a corporate director of ManpowerGroup.

Then there’s the issue of racism, even when it’s not overt. The study “Being Black in Corporate America” by the Center for Talent Innovation found a majority of black professionals have experienced racial prejudice at work, more than any other group.

It often comes through so-called microaggressions, such as being told you’re not like others of your race or that you’re “articulate.”

“The prejudice and microaggressions carry consequences,” the report noted. “In addition to low representation and slow advancement, we also find a bigger risk of attrition among black professionals: more than a third intend to leave their companies within two years.”