Puschmann Paul, Donrovich Robyn, Matthijs Koen
Radboud Group for Historical Demography and Family History, Department of History, Radboud University, Erasmusplein 1, 6525, HT, Nijmegen, the Netherlands.
Family and Population Studies, Centre for Sociological Research, KU Leuven, Parkstraat 45, 3000, Leuven, Belgium.
Hum Nat. 2017 Dec;28(4):481-499. doi: 10.1007/s12110-017-9303-1.
The purpose of this research is to empirically test the salmon bias hypothesis, which states that the "healthy migrant" effect-referring to a situation in which migrants enjoy lower mortality risks than natives-is caused by selective return-migration of the weak, sick, and elderly. Using a unique longitudinal micro-level database-the Historical Sample of the Netherlands-we tracked the life courses of internal migrants after they had left the city of Rotterdam, which allowed us to compare mortality risks of stayers, returnees, and movers using survival analysis for the study group as a whole, and also for men and women separately. Although migrants who stayed in the receiving society had significantly higher mortality risks than natives, no significant difference was found for migrants who returned to their municipality of birth (returnees). By contrast, migrants who left for another destination (movers) had much lower mortality risks than natives. Natives who left Rotterdam also had significantly lower mortality risks than natives who stayed in Rotterdam. Female migrants, in particular, who stayed in the receiving urban society paid a long-term health price. In the case of Rotterdam, the salmon bias hypothesis can be rejected because the lower mortality effect among migrants was not caused by selective return-migration. The healthy migrant effect is real and due to a positive selection effect: Healthier people are more likely to migrate.
本研究的目的是对“鲑鱼偏差假说”进行实证检验，该假说认为，“健康移民”效应（即移民的死亡率风险低于本地居民的情况）是由体弱多病和年老的移民选择性返乡所致。我们利用一个独特的纵向微观层面数据库——荷兰历史样本，追踪了内部移民离开鹿特丹市后的生命历程，这使我们能够通过生存分析，对整个研究组以及分别对男性和女性的留居者、返乡者和迁移者的死亡风险进行比较。虽然留在迁入社会的移民的死亡风险显著高于本地居民，但对于返回其出生市镇的移民（返乡者），未发现显著差异。相比之下，前往另一个目的地的移民（迁移者）的死亡风险远低于本地居民。离开鹿特丹的本地居民的死亡风险也显著低于留在鹿特丹的本地居民。尤其是留在迁入城市社会的女性移民付出了长期的健康代价。就鹿特丹而言，“鲑鱼偏差假说”可以被否定，因为移民中较低的死亡效应并非由选择性返乡所致。“健康移民”效应是真实存在的，且归因于积极的选择效应：更健康的人更有可能迁移。
