Influence of a research career on the scientific productivity and impact of Spanish researchers: the cumulative advantage role

Careers in research can have a significant effect on the chances of scientists' success. This effect, also known as cumulative advantage, contributes to skewing the unequal distribution of both production and impact among scientists. This paper focuses on determining whether the cumulative advantage is present within a sample of 174 Spanish scientists doing research in four major areas (i.e.: physics, chemistry, biology and biochemistry). In order to determine the impact of their careers in research, we specify a multi-equational model. Among other variables, we include those related with their doctoral training, the postdoctoral period and the quality of the departments where scientists are hired after they finish their post doctoral work. Moreover, the model includes a group of hypotheses gathered from a survey of the literature on this topic. The model is based on the Path Analysis technique. We also have developed a method to determine the quality of academic departments using a single scale suitable for any country and discipline. The main result confirms the existence of cumulative advantage being the predoctoral productivity the main determinant of productivity during the ten years after obtaining the doctor degree. Finally, a bias in productivity and impact in favour of men is observed.