Invisible emigrants: A research note on over-coverage bias from unrecorded migrant departures in socio-demographic...

This research examines the impact of population over-coverage on socio-demographic indicators for international migrants in Sweden. Over-coverage occurs when emigrants or deceased individuals remain in population registers, leading to overestimation of the resident population. This particularly affects migrants due to the increasing prevalence of return, onward, and circular migration. As register-based data collection becomes prevalent, addressing over-coverage bias is critical. Using multiple systems estimation models, we adjust for over-coverage in Swedish population registers and calculate accurate demographic and socio-economic rates. We use administrative data for 2003-16 to compute age-specific fertility rates, mortality rates, employment/unemployment rates, Total Fertility Rates, and life expectancy for migrants. Results demonstrate that over-coverage substantially affects demographic and economic indicators, particularly at typical migration ages, with mortality rates showing the largest bias at older ages. Findings highlight the importance of addressing over-coverage to improve the reliability of socio-demographic insights from register-based population systems.