Figure 2. Number of use of specific tag types by publication decade.

Total number of tag use (n = 271) exceeds that of reviewed papers (n = 207) because many studies used more than one tag type. The category “T-Bar” includes carlin, cinch, spaghetti, Floy, and Petersen disk tags. The plot does not include data from a paper published in 1940 because the tag type used was not specified by the author.