Low immigrant mortality in England and Wales: selection or data artefact? Findings from the ONS Longitudinal Study 1971-2001

Matthew Wallace, University of Liverpool
Hill Kulu, University of Liverpool

Previous research shows low mortality for some migrant groups compared to natives in the host country. This advantage is often attributed to health selection processes in immigration, emigration and re-migration, and to protective health behaviours among migrants. Little research has examined the role of data issues, especially the registration of moves. If return migration from the host country is under-recorded, the moves produce a numerator-denominator bias leading to under-estimation of migrant mortality (‘data artefact’). The paper investigates the mortality of immigrants in England and Wales from 1971-2001 using the Office for National Statistics Longitudinal Study (ONS LS), a 1% sample of the population of England and Wales (sample size: 450,000 individuals). We apply parametric survival analysis with a Gompertz specification of baseline mortality. We conduct a series of sensitivity analyses to assess the impact of both entry and exit uncertainty on immigrant mortality rates. The analysis shows that most international migrants have lower mortality than England and Wales natives. Differences largely persist when we adjust models to entry and exit uncertainty and they become pronounced once we control for socioeconomic characteristics. This study supports low mortality among immigrants in England and Wales and importantly, shows that results are not data artefact.