In this text, we analyze the limitations of using academic age as a proxy for biological age in the whole national science system, for which we consider both biological age and academic age of all researchers from all Polish universities, holding at least a PhD degree and participating in global academic science through international publications (N = 20 569). An approximation of a researcher's functioning in global science is having at least one publication indexed in the Scopus database in the analyzed decade 2009–2018. Thus, using the example of comprehensive data from the entire national system of science, we estimate the extent of limitations of using academic age as a proxy for biological age depending on selected independent variables and analyze both the practical and methodological implications of using academic age in academic career research, which is one of the most important components of quantitative studies of science.

The purpose of this article is to determine what can we learn about the changing demographics of scientific personnel around the world and over time using available global bibliometric data sources. We wanted to see how useful global data could be for analyzing the scientific workforce. We tested how the demographic transformation of the global scientific profession can be measured using new data sources, thus transcending the traditional approach in which national statistics from national statistical offices are aggregated to a higher level, as in the case of the scientific workforce databases produced by the OECD, UNESCO and the European Union (Eurostat).