Why do startups become unicorns instead of going public?

Unicorns are startups that choose to stay private even though they are large enough to go public. We propose an efficiency explanation for their existence. Startups relying highly on organization capital are more vulnerable to expropriation of their organization capital if they go public before their position is sufficiently secure. Our main empirical findings are that shocks to the fragility of organization capital decrease the IPO likelihood, unicorn status enables startups to stay private longer by giving them access to new sources of capital, and unicorns and their industries have higher organization capital intensity than other startups.