Abel Ernest L, Kruger Michael L
Department of Obstetrics/Gynecology, Wayne State University, Detroit, Michigan, USA.
Soc Biol. 2005 Spring-Summer;52(1-2):47-55.
We examined two alternative explanations, one demographic, the other sociological, for the uneven distribution of birth months of Major League baseball (MLB) players active between 1880 and 1999. Beginning in 1900, players born between August and October were significantly overrepresented, and this uneven distribution was almost identical for the next five 20-year periods. During the last 20-year period (1980-1999), the disparity in birth months became even more pronounced. Ethnicity, handedness, player position, accomplishment (winning an award), and career length were not significantly related to birth month. Prior to 1980, the distribution of births for MLB players did not differ significantly from the distribution for the general population, but after 1980, it did. We concluded that up until 1980, the uneven distribution of birth months in MLB originated in the demographic seasonality-related excess number of births in August and September in the United States. Beginning in the 1980s, this seasonality pattern was institutionally reinforced by the growing influence of Little League and related junior baseball leagues and their reliance on the August 1 birth date for age grouping.
我们研究了两种关于1880年至1999年间活跃的美国职业棒球大联盟（MLB）球员出生月份分布不均的解释，一种是人口统计学解释，另一种是社会学解释。从1900年开始，8月至10月出生的球员人数显著过多，并且在接下来的五个20年时间段内，这种分布不均几乎相同。在最后一个20年时间段（1980 - 1999年），出生月份的差异变得更加明显。种族、用手习惯、球员位置、成就（获奖）和职业生涯长度与出生月份均无显著关联。1980年之前，MLB球员的出生分布与普通人群的分布没有显著差异，但1980年之后则有差异。我们得出结论，直到1980年，MLB中出生月份的分布不均源于美国8月和9月与人口统计学季节性相关的出生人数过多。从20世纪80年代开始，这种季节性模式因小联盟及相关少年棒球联盟的影响力不断增强以及它们对8月1日出生日期进行年龄分组的依赖而在制度上得到强化。
