Skewed sex ratios have been found to increase crime and spread of diseases, as well as influence fertility decisions, gender roles, and economic development. I document the extent to which international and internal migration shape national and subnational sex ratios among young adults (SRYA). For this purpose, I analyze the data from the United Nations’ Urban and Rural Population by Age and Sex and World Population Prospects, focusing on the cohort born between 1975 and 1985 in 200 countries. I find that, while 33 countries have significantly skewed country-level sex ratios, as many as 107 of the 200 investigated countries have either rural or urban skewed SRYA in 2010. To identify the sources of sex ratio imbalances, I decompose country-level sex ratios into three factors: sex ratio at birth, relative probability of survival, and sex-selective migration. I show that without sex-selective international migration, country-level SRYA would be balanced in almost all countries of the world. In the third part of the study, I use Eurostat data for European subnational regions. I find a strong log-linear relationship between sex ratios and population density, that is, relatively more women among young adults as population density increases. Moreover, I show that skewed SRYA can be mainly attributable to sex-selective migration, rather than to imbalanced sex ratios at birth and differential mortality.

中文翻译：

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年轻人的移民和地方性性别比例失衡

人们发现，性别比例失衡会增加犯罪和疾病传播，并影响生育决策、性别角色和经济发展。我记录了国际和国内移民在多大程度上影响了国家和地方的年轻人性别比例（SRYA）。为此，我分析了联合国《按年龄和性别划分的城乡人口》和《世界人口展望》的数据，重点关注 200 个国家 1975 年至 1985 年间出生的人群。我发现，虽然有 33 个国家的国家级性别比例存在显着偏差，但 200 个调查国家中，有多达 107 个国家在 2010 年存在农村或城市 SRYA 偏差。为了确定性别比例失衡的根源，我分解了国家级性别比例将比率分为三个因素：出生性别比、相对生存概率、和性别选择性迁移。我表明，如果没有性别选择性的国际移民，世界上几乎所有国家的国家级 SRYA 都将是平衡的。在研究的第三部分中，我使用了欧洲统计局关于欧洲次国家地区的数据。我发现性别比和人口密度之间存在很强的对数线性关系，也就是说，随着人口密度的增加，年轻人中女性的数量相对较多。此外，我发现 SRYA 的倾斜主要归因于性别选择性移民，而不是出生性别比失衡和死亡率差异。我发现性别比和人口密度之间存在很强的对数线性关系，也就是说，随着人口密度的增加，年轻人中女性的数量相对较多。此外，我发现 SRYA 的倾斜主要归因于性别选择性移民，而不是出生性别比失衡和死亡率差异。我发现性别比和人口密度之间存在很强的对数线性关系，也就是说，随着人口密度的增加，年轻人中女性的数量相对较多。此外，我发现 SRYA 的倾斜主要归因于性别选择性移民，而不是出生性别比失衡和死亡率差异。