10.17045/sthlmuni.7000907.v2 Andrea Fuentes Monti Andrea Fuentes Monti Sven Drefahl Sven Drefahl Eleonora Mussino Eleonora Mussino Juho Härkönen Juho Härkönen Over-coverage in Swedish Population Registers Leads to Bias in Demographic Estimates Stockholm University 2018 Stockholm Research Reports in Demography Sociologiska institutionen Department of Sociology SUDA Stockholm University Demography Unit Stockholms universitets demografiska avdelning Over-coverage Fertility Demography not elsewhere classified 2018-09-03 08:36:58 Preprint https://su.figshare.com/articles/preprint/Over-coverage_in_Swedish_Population_Registers_Leads_to_Biasin_Demographic_Estimates/7000907 Abstract: Estimating the number of individuals that live in a country has always been among the essential tasks for demographers. In this study we assess the potential bias in estimating the size of different migrant populations due to over-coverage in a country’s population-register system. Over-coverage, i.e., from individuals registered but not living in a country, constitutes an increasingly pressing phenomenon and is tightly linked to differential patterns of registered emigration. However, there is no common understanding on how to deal with over-coverage in demographic estimates and research. This study examines different approaches to over-coverage estimation and discusses ways of improving current estimation methods using Swedish total population register data for the years 1990-2012. We assess over-coverage levels across migrant groups, test how estimates of age-specific fertility and mortality are affected when adjusting for over-coverage, and examine whether over-coverage can explain parts of the healthy migrant paradox. Our results confirm the existence of over-coverage. When adjusting for over-coverage, we find substantial changes in mortality and fertility rates for people in migrating ages. Our results suggest that accounting for over-coverage is particularly essential for correctly estimating fertility in migrant populations.