Department of Human Sciences, Faculty of Letters, Nara Women's University, Kitauoya-nishi-machi, Nara City, 630-8506, Japan.
National Institute for Physiological Sciences, Japan.
Percept Mot Skills. 2013 Aug;117(1):1318-31. doi: 10.2466/10.25.pms.117x13z1.
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.
本研究调查了相对年龄效应（出生日期的偏差分布）在 1911 年至 1980 年出生的日本职业棒球运动员中的存在。日本在体育和教育方面采用了独特的年度年龄分组，即从次年的 4 月 1 日至 3 月 31 日。因此，运动员根据出生月份分为四个季度：Q1（4 月至 6 月）、Q2（7 月至 9 月）、Q3（10 月至 12 月）和 Q4（次年 1 月至 3 月）。在 20 世纪 40 年代和随后几十年出生的运动员中，存在着统计学上的出生日期偏差分布（中等效应），而在 20 世纪 10 年代、20 年代和 30 年代出生的运动员中也观察到了类似的（但较小的）相对年龄效应。相对年龄效应的大小随时间而变化，国际竞争和媒体报道等社会文化因素可能对此效应有很大影响。
