The new public management paradigm, the raise of the number of students and a stronger international competition in attracting external funds for large research projects have lead universities to increase the number and role of non-academics. Non-academic staff may be beneficial to university performance if it supports the main activities carried out by the academic staff. On the other hand, it may be detrimental for university performance if it translates in an increase of administrative burden. We shed new lights analyzing European and US universities. We consider the heterogeneity of non-academic staff as an “unobserved” factor and estimate it non-parametrically. We find indeed some differences of unobserved heterogeneity between Europe and the US. In the case of US universities, the latent variable is positively correlated with publication activity and core funding, while, for Europe, the relationships are inverse.