Figure 2. Change in the frequency over time for the topics for which temporal change was significant at the Bonferroni-adjusted level (p<0.001) in at least one of the datasets.

White bars denote ‘all journals’ and gray bars denote ‘core journals’. *** Temporal trend was significant (a logistic model, see Table 2), p<0.001. ** p<0.01. * p<0.05.