In this work we investigate the determinants of professors' career advancement in Italian universities. From the analyses, it emerges that the fundamental determinant of an academic candidate's success is not scientific merit, but rather the number of years that the candidate has belonged to the same university as the selection committee president. Where applicants have participated in research work with the president, their probability of success also increases significantly. The factors of the years of service and occurrence of joint research for the other commission members also have an effect, however of lesser weight. The specific phenomenon of nepotism, although it exists, seems less important. The scientific quality of the commission members has negligible effect on the expected outcome of the competition, and even more so the geographic location of the university calling for the competition.