How does birth order and number of siblings effect fertility? A within-family comparison using Swedish Register Data

Kathrin Morosow, Stockholm University
Martin Kolk, Stockholm University

This study uses Swedish register data to estimate two research questions, (1) possible birth order effects on fertility outcomes and (2) if intergenerational transmission of fertility differs by birth order. To answer these questions we apply two novel methodological approaches. For our first research question we use sibling comparisons, and for our second question we stratify our population by birth order. The estimations are based on all fully biologically related siblings in Sweden whose mothers were born between 1915-1935 (N=1,475,177). We further examine if there are gender differences for these relationships. Results show that higher birth order has a small negative effect on completed fertility. Parent’s completed fertility shows a positive effect on the younger generation’s completed fertility, which is stronger for earlier than for later born. Women display stronger differences by birth order than men for both our research questions.