The consequence of birth spacing for first- and second-born siblings’ long-term income rank: A restrictive two-child family approach

Keywords: birth spacing, income rank, population register data, Sweden


Birth spacing between siblings may have long-lasting impacts on them. This paper focuses on how different birth-spacing intervals are associated with income rank during the ages 33 to 42 years. In order to disentangle birth spacing from birth order, while holding potential sibsize association constant, an interaction model is used on a restrictive subpopulation of two-child families born between 1960 and 1970. The results show clear differences between first- and second-born siblings. Increased birth spacing, up to 3 years, is positively associated with first-born siblings’ income rank. Birth spacing has a negligible association with second-born siblings, at the common spacing intervals (less than 5 years). Having relatively high spacing intervals (over 5 years) is associated with somewhat lower income-rank than having mid-length intervals for both first- and second-born siblings.