That's actually a very interesting point. I know Mark Zuckerberg owned a really big chunk (~30%) of FB when they IPO'd. Anyone with insight know if the norm is closer to Zuckerberg or Levie?
Realize they've raised at least $414M that has been reported.
At many of those rounds it was likely possible for founders/ early employees to cash out options. FB/ Mark had enormous leverage because it was an unstoppable growth machine. Box is a great company, but still has to battle to grow sales into revenue/ profits, as is evidenced by the S-1.
The remaining 93.9% belonged to the founders, the Board, the employees, and friends and family. Everyone listed on the S-1, with one exception, took a bit off the top but held on to most of their shares.
The one exception was Bill Gates's sister's trust fund, which owned 20,000 shares -- 0.1% of the company. She could've been a hundred-millionaire if she'd held on to it, but her trustee sold it for $400,000 and moved on.