But lawsuits and appeals take time and money, and there's no guarantee of data waiting at the end of the road. Mike Swift, a reporter with the San Jose Mercury News, began probing the topic in 2008 by sending similar FOIA requests for data from the region's 15 largest employers.

His inquiry sparked a two-year legal battle, resulting in access to data from just one company -- HP -- that had opposed its release.

The Black Economic Council and the National Asian American Coalition have also attempted to uncover diversity data at major companies, but most of those requests have turned up little information.

"Companies are happy to hide behind a law that provides so little access to this data," said Sims, the law professor. "Tech is the most vibrant sector of the American economy, and rather than trying to fix problems, they want to keep secrets."