The Effect of Marriage on Mortality: Selection or Protection? Evidence from Danish Twins Using Fixed-Effect Survival Models

Iliana Kohler, Max Planck Institute for Demographic Research

A robust finding in the demographic research is that married people have a lower risk of death as compared to divorced or single individuals. Two main hypotheses have been proposed to explain this relationship between marriage and mortality - marital selection versus marital protection. In this paper I investigate this interdependence between marriage and mortality by proposing new statistical methods and data. My analyses are based on the Danish twin register. I focus on MZ twins that share the same genetic determinants of mortality and same socioeconomic background during childhood. I develop fixed-effect survival models that to my knowledge have not been applied to the analysis of mortality and twin data. My fixed-effect survival model allows the estimation of the parameter of interest, which measures the impact of individual characteristics on the level of mortality, without imposing the assumption of independence between the distribution of unobserved heterogeneity and individual characteristics.