After weeks of scandal, Uber released its first report Tuesday detailing the gender breakdown and racial makeup of its employees.

Though welcomed by diversity advocates, the revelations weren't that surprising: Within engineering, only 15 per cent are women and 6 per cent are black, Latino or multiracial, which makes Uber not that different from other tech companies, where those groups make up a tiny fraction of the technical workforce.

In fact, the more illuminating piece of data about diversity at Uber isn't in its report at all.

Retention – the percentage of each demographic group that stays at the company each year – reveals more about the hospitality of the workplace culture than the percentage of white and Asian men there overall.

Most companies, including Uber and its peers in Silicon Valley, track it. They just don't make it public.

Retention data is a proxy for job satisfaction, and tech companies won't be able to build the diverse workforces they claim to be working towards unless they can hold on to the small fraction of female and minority employees they successfully recruit.

Since 2014, demographics at Apple, Facebook, Google, Twitter and others have stayed roughly the same: Women make up about 17 per cent of technical workers; only about 6 per cent are black or Latino.

Across industries, few companies release employee retention data, but tech firms have consistently held themselves up as meritocracies, based on data-focused decision-making.

At the same time, they've assembled homogeneous employee bases, and come under fire for tolerating behaviour and attitudes that make minorities feel unwelcome.

As far as data and transparency, they have mostly stuck to releasing annual demographic breakdowns and the occasional tidbit about the race and gender of new hires.

"People are looking for ways to tell a good story around their diversity and inclusion efforts," said Ellen Pao, co-founder of Project Include, which advocates for more diversity in Silicon Valley.

"The fact that tech companies aren't sharing their retention numbers indicates those numbers likely aren't good."

Bloomberg