Hashtag popularity decay in terms of total number of tweets and users associated with each tag. On the horizontal axis tags have been ordered according to one of the two popularity measures: number of tweets (bottom) and users (top). The roughly exponential decay indicates that the inclusion of additional hashtags is unlikely to result in a substantial increase in the size of the corpus.
Conover et al. EPJ Data Science 2012 1:6 doi:10.1140/epjds6