For several years, Uber withheld its diversity figures from the public--the most notable company in tech to do so--but faced with multiple major crises, the company finally released these figures this week.

Now the attention that was focused on Uber turns to the remaining holdouts. The biggest tech companies that have yet to open up their diversity books include private "unicorns" like Lyft, Instacart, and Spotify and companies that have only recently gone public, such as Square, Box, Snap, Twilio, and Tesla.

"These reports provide transparency for stakeholders," says Kyle Graden, director of community engagement and education at Open for Service, a nonprofit that helps consumers find non-discriminatory businesses and service providers.

"Whether deciding to invest, join the company, or become a customer, every person has their own values to assess when making a decision," Graden says. "Releasing the reports shows effort to respond to concerns about the lack of diversity in tech."

Since 2014, most tech companies of note have shared these reports. That includes giants like Apple, Google, and Facebook and smaller players like Slack, Pinterest, and Twitter. Pretty much across the board, the numbers aren't great, but by providing these figures to the public on an annual basis, these companies are holding themselves accountable to their commitments to build diverse workplaces.

"Research shows that companies that are more diverse are financially more successful," says Michael Connor, executive director at Open MIC, a nonprofit that pushes for more diversity within tech companies. "You could ignore those findings, but why be stupid?"

Among the noteworthy holdouts, there are varying levels of commitment toward diversity. Some have indicated that reports and genuine diversity efforts are underway. Others have hired heads of diversity. And some have not made indications that diversity is a priority at all.

Bringing up the rear would be Tesla, Snap, and Twilio.

The car manufacturer has yet to release a diversity report. The company was recently hit with separate lawsuits from a female employee and a black employee, both of whom alleged harassment and discrimination that held back their careers.

Snap, too, has been criticized for its lack of commitment toward diversity. Every couple of months, it seems, the company draws the ire of users with augmented reality lenses for Snapchat that play to stereotypes. The company has previously said that diversity is a topic that matters, and Jarvis Sam, the company's head of diversity, has spoken at conferences like Tech Inclusion. Nonetheless, Snap has not committed to releasing a diversity report nor has it given much insight into what it's doing to foster a workplace that's diverse and inclusive.

Likewise, Twilio has often participated in diversity conferences, but the company has never published a diversity report. Asked if there were any plans to do so, a company spokeswoman says Twilio had no news to share. Instead, the company points to the recent hiring of LaFawn Davis, its new head of diversity.

Neither Tesla nor Snap responded to requests for comment. Shares of Tesla, Snap, and Twilio are all traded in the public stock market.

For companies like these, experts warn that they may want to take a serious look at addressing their diversity woes before they boil over publicly.

"Consider what's happened Uber," Connor says. "Ask yourself: Do we not want to know what's going on with our work force?"

Then there's Instacart.

Speaking at TechCrunch Disrupt in September, CEO Apoorva Mehta committed his company to releasing a diversity report within the next couple of months. More than six months later, no such thing has happened. Asked if Instacart still plans to release a report, a spokeswoman for the company tells Inc. that Instacart will "probably" release a report but offered no date for when that might occur.

Putting together a diversity report is "a big project, and we just haven't had the bandwidth to do it," a spokeswoman for the company says.

Despite this backpedaling, Instacart has been working on making sure it executes good diversity practices. The spokeswoman says the company has put all employees through unconscious bias training and that leaders have undergone inclusivity in management training. The company has also launched employee resources groups, such as Women at Instacart, and it often holds diversity workshops and brings in relevant speakers, such as Rachel Williams, Yelp's head of diversity.

The remaining holdouts have expressed much stronger commitments to diversity.

Last summer, for example, Lyft, Box, and Spotify pledged to President Obama that they would work on bringing diversity and inclusion to their work forces and promised to publish goals for recruiting and annual data on the diversity of their companies. None of the companies has actually followed through as yet, but the pledge is there.

Lyft, for example, says its diversity report will be coming "in the near future," while Box tells Inc. that a report will be coming "later this year." Spotify, however, did not responded to a request for comment.

Square did not take the Tech Inclusion Pledge, but when reached by Inc., the public tech company said that it planned to release its first diversity report in the "next couple of months."

While diversity experts advocate for companies to publish diversity reports, they also caution that these documents are simply barometers. Just as SEC filings give investors a sense of a company's financial health, these reports give a sense of a company's state of diversity. But they alone cannot fix a company's lack of diversity.

"I don't think releasing a report is the most important thing you can do," says Joelle Emerson, CEO of Paradigm, a consulting firm focused on helping tech companies improve their diversity. "The most important thing you can do is actually analyzing your data internally and putting strategies in place."