Background: One’s number of siblings is an important determinant of many life outcomes, such as educational attainment. In the last century the United States has experienced a ‘sibsize revolution’, in which sibship sizes declined, and which led to a convergence in family circumstances for children. Did this happen in other countries as well? Objective: This study examines the development of sibship size and social disparities in sibship size in low-fertility countries across the 20th century. Methods: We analyze sibship size data collected from 111 nationally representative surveys conducted in 26 low-fertility countries across the 20th century. Results: Average sibship sizes have declined in virtually all countries. Average sibship sizes are socially stratified, with smaller sibship sizes among higher-educated parents. This social disparity in sibship size has declined over time, indicating convergence in most countries. This convergence applies to large families, but not to only-child families. Contribution: Siblings are an understudied phenomenon in family demography, despite their growing importance in a time of increasingly complex family structures. Given the significance of sibship size for children’s educational outcomes and overall life chances, decreasing social disparities in sibship size suggest greater equality in the intergenerational transmission of advantage.

中文翻译：

---

国际背景下的同胞革命：26个国家中同胞人数的社会差距正在缩小

背景：同胞的数量是许多生活成果（例如受教育程度）的重要决定因素。在上个世纪，美国经历了一场“同父异母的革命”，同胞的大小有所减少，导致儿童家庭环境的趋同。这在其他国家也发生了吗？目的：本研究探讨了20世纪低生育率国家同胞人数的发展和同胞人数的社会差距。方法：我们分析了从20世纪26个低生育率国家中进行的111个全国代表性调查收集的同胞大小数据。结果：几乎所有国家的平均同胞关系规模都有所下降。平均同胞大小在社会上是分层的，受过高等教育的父母中较小的同胞大小。随着时间的流逝，同胞关系的社会差距有所减少，这表明在大多数国家中趋同。这种融合适用于大家庭，但不适用于独生子女家庭。贡献：兄弟姐妹是家庭人口统计学中被忽视的现象，尽管在家庭结构日益复杂的时代，兄弟姐妹的重要性日益提高。考虑到同胞人数的大小对儿童的教育成果和整体生活机会的重要性，减少同胞大小的社会差距意味着代际利益的更大平等。尽管在家庭结构日益复杂的时代，他们的重要性越来越高。考虑到同胞人数的大小对儿童的教育成果和整体生活机会的重要性，减少同胞大小的社会差距意味着代际利益的更大平等。尽管在家庭结构日益复杂的时代，他们的重要性越来越高。考虑到同胞人数的大小对儿童的教育成果和整体生活机会的重要性，减少同胞大小的社会差距意味着代际利益的更大平等。