title: Relative age effects in Japanese baseball: an historical analysis.
abstract: The present study investigated the existence of the relative age effect, a biased distribution of birth dates, in Japanese professional baseball players born from 1911 to 1980. Japan applies a unique annual-age grouping for sport and education, which is from April 1 to March 31 of the following year. Thus, athletes were divided into four groups based on their month of birth; quarters Q1 (April-June), Q2 (July-September), Q3 (October-December), and Q4 (January-March of the following year). There were statistically biased distributions of birth dates among players born in the 1940s and subsequent decades (medium effects), and similar (but small) relative age effects were observed among players born in the 1910s, 1920s, and 1930s. The magnitude of the relative age effect changed with time, and socio-cultural factors such as international competition and media coverage may have contributed greatly to this effect.
authors.affiliation: Department of Human Sciences, Faculty of Letters, Nara Women's University, Kitauoya-nishi-machi, Nara City, 630-8506, Japan. hiroki-nakata@cc.nara-wu.ac.jp
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakata
authors.affiliation: National Institute for Physiological Sciences, Japan.
authors.forename: Kiwako
authors.initials: K
authors.lastname: Sakamoto
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D054874:Athletic Performance; D001484:Baseball / Q000266:history*; D003163:Competitive Behavior; D003431:Cross-Cultural Comparison; D049673:History, 20th Century; D006801:Humans; D007564:Japan; D008297:Male; D055815:Young Adult