Fig. 2

Publication year of papers. The black bar shows the whole number of papers published in the year. The orange bar represents the top5% in citation normalised by the average number of citations of papers submitted in the same field in the same year (Radicchi et al. 2008). The small graph shows the proportion of top papers to the total number of papers submitted in each year, which was stable at around 0.05 for papers in the period when there was sufficient time to obtain citations