  How difficult is it for an early career academic to climb the ranks of their
discipline? We tackle this question with a comprehensive bibliometric analysis
of 57 disciplines, examining the publications of more than 5 million authors
whose careers started between 1986 and 2008. We calibrate a simple random walk
model over historical data of ranking mobility, which we use to (1) identify
which strata of academic impact rankings are the most/least mobile and (2)
study the temporal evolution of mobility. By focusing our analysis on cohorts
of authors starting their careers in the same year, we find that ranking
mobility is remarkably low for the top and bottom-ranked authors, and that this
excess of stability persists throughout the entire period of our analysis. We
further observe that mobility of impact rankings has increased over time, and
that such rise has been accompanied by a decline of impact inequality, which is
consistent with the negative correlation that we observe between such two
quantities. These findings provide clarity on the opportunities of new scholars
entering the academic community, with implications for academic policymaking.
