We study failures between 1993 and 2017 in the complete population of 1731 English and Scottish university spinoffs founded since 1977. We borrow and expand the concept of density dependence from organizational ecology to theorize that a spinoff's propensity to fail is affected by the number of spinoffs active not only in the aggregate population but also within its parent university's portfolio. We contribute to organizational theory, demonstrating the importance of organizational groups that form within larger populations on individual organizations' propensity to fail. We contribute to literature on academic entrepreneurship showing that, for most universities, spinoff portfolio growth can lower associated spinoffs' failure rates, but that such effects need to be juxtaposed to the aggregate population's finite capacity to support an expanding number of spinoffs.

我们研究了 1993 年至 2017 年间自 1977 年以来成立的 1731 所英格兰和苏格兰大学衍生公司的全部失败情况。我们借用并扩展了组织生态学中的密度依赖概念，得出理论认为，衍生公司的失败倾向受到活跃衍生公司数量的影响不仅在总人口中，而且在其母大学的投资组合中。我们对组织理论做出了贡献，证明了在较大群体中形成的组织群体对单个组织失败倾向的重要性。我们为学术创业文献做出的贡献表明，对于大多数大学来说，分拆投资组合的增长可以降低相关分拆的失败率，