Low immigrant mortality in England and Wales: a data artefact?

Previous research shows low mortality for most immigrants compared to natives in host countries. This advantage is often attributed to health selection processes in migration and to protective health behaviours. Little research has examined the role of data quality, especially the registration of moves. Registration errors relating to moves between origin and host countries can mismatch deaths and risk populations, leading to denominator bias and an under-estimation of migrant mortality (data artefact). The paper investigates the mortality of immigrants in England and Wales from 1971 to 2001 using the Office for National Statistics Longitudinal Study (ONS LS), a 1% sample of the population of England and Wales. We apply parametric survival models to study the mortality of 450,000 individuals. We conduct sensitivity analysis to assess the impact of entry and exit uncertainty on immigrant mortality rates. The analysis shows that most international migrants have lower mortality than natives in England and Wales. Differences largely persist when we adjust models to entry and exit uncertainty and they become pronounced once we control for individual socioeconomic characteristics. This study supports low mortality among immigrants and shows that results are not a data artefact.