The paper makes three contributions to the economics literature on entrepreneurship. We offer a new measure of entrepreneurship which accounts for variations in persistence in self-employment. We outline an econometric methodology to account for this approach and find that it is superior to probit/logit models which have dominated the literature. While our results indicate that this existing literature is good at explaining an individual's propensity to try self-employment, we find that entrepreneurial persistence is determined by a different model and unearth some new insights into the roles of early career experience, finance, role models, gender and the unemployment push effect.