National Venture Capital Association data showed that the average time from funding to exit (via an acquisition or an IPO) increased dramatically from 3.1 years in 2001 to 6.8 years by 2014. Those figures count all exits, including many that did not generate a positive return for investors or founders. When EquityZen limited its analysis to only those startups that had an IPO (and thus, almost definitely generated returns for at least its investors and probably most founders, too), it found that from founding to public offering takes an average of eleven years.
