 This is motivated by the idea that while the average number of “old” citations per paper is stable (cf. Sec. 3.2), they might be distributed in an unbalanced way.
future work includes a deeper qualitative analysis of which (type of) papers are being cited; a more fine-grained analysis of different research topics in NLP to determine whether changes are more prevalent within certain areas than others; or extending the analysis to a larger set of the papers in the ACL Anthology.