Birth Month Mortality Puzzles in Norway

Iliana V. Kohler, University of Pennsylvania

We analyze the association of birth month with mortality above age 50 in Norway. Utilizing the geographic, climatic and socioeconomic diversity of Norway, we investigate possible pathways linking birth month to mortality at older ages. We investigate whether birth month effects in mortality operate trough social mechanisms such as relative age class effects (i.e., educational differences related to relative age within the school cohort). The analyses use data from the Norwegian population register. We estimate only for Southern and Eastern Norway strong association of birth month with mortality for cohorts born 1900-1914. Controlling for completed level of education does not alter this pattern suggesting that birth month effects do not reflect differences in relative age class. The geographic pattern of birth month effects in mortality suggests that environmental differences such as exposure to infectious diseases may explain the association of birth month with mortality in late life.