The skewness of scientific productivity

This paper exploits a unique 2003-2011 large dataset, indexed by Thomson & Reuters, consisting of 17.2 million disambiguated authors classified into 30 broad scientific fields, as well as the 48.2 million articles resulting from a multiplying strategy in which any article co-authored by two or more persons is wholly assigned as many times as necessary to each of them. We measure individual productivity in two ways: as the number of articles per person, and as the mean citation per article per person in the 2003-2011 period. We analyze the shape of the two types of individual productivity distributions in each field using sizeand scale-independent indicators. For productivity inequality, we use the coefficient of variation. To assess the skewness of productivity distributions we use a robust index of skewness, as well as the Characteristic Scores and Scales approach. In each field, we study two samples: the entire population, and what we call “successful authors”, namely, the subset of scientists whose productivity is above their field average. The main result is that, in spite of wide differences in production and citation practices across fields, the shape of field productivity distributions are very similar across fields. The parallelism of the results for the population as a whole and for the subset of successful authors when productivity is measured as mean citation per article per person, reveals the fractal nature of the skewness of scientific productivity in this case. These results are essentially maintained when any article coauthored by two or more persons is fractionally assigned to each of them. Acknowledgements. This is the second version of a working paper which appeared in February in this series under the same title. The paper was conceived while Ruiz-Castillo enjoyed the hospitality of the Centre for Science and Technology Studies, Leiden University, The Netherlands, during the 2013 spring term. Ruiz-Castillo also acknowledges financial help from the Spanish MEC through grant ECO2010-19596. The authors acknowledge fruitful conversations with Raquel Carrasco, as well as comments from the participants in a CWTS seminar. All remaining shortcomings are the sole responsibility of the authors.