Fig. 3

Topic trend plot; the 5 topics with the strongest positive trend (a) or strongest negative trend (b); the slope rank of 1 indicates that the slope of the linear trend line has the highest overall value and a rank of 300 indicates the lowest value; dots represent the mean topic probability per year; the solid lines show AICc-optimized LOESS-smoothed trend lines; the dashed lines show the linear trend lines based on fitting linear models on the topic probabilities per year (not the mean values); since publication rates increase over the years (see Fig. 1b), the recent years have a stronger influence on the linear trend lines than earlier years