A history of effect size indices

Depending on how one interprets what an effect size index is, it may be claimed that its history started around 1940, or about 100 years prior to that. An attempt is made in this article to trace histories of a variety of effect size indices. Effect size bases discussed pertain to (a) relationship, (b) group differences, and (c) group overlap. Multivariable as well as univariate indices are considered in reviewing the histories.