On the genetic bias of the quarter of birth instrument
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Updated: Mar 25, 2026

Genotyping Single Nucleotide Polymorphisms in the Mitochondrial Genome by Pyrosequencing
Published on: February 10, 2023
Cornelius A Rietveld1, Dinand Webbink2
1Erasmus School of Economics, Erasmus University Rotterdam, Rotterdam, The Netherlands; Erasmus University Rotterdam Institute for Behavior and Biology, Erasmus University Rotterdam, Rotterdam, The Netherlands; Tinbergen Institute, The Netherlands.
Abstract:
Many studies in economics use quarter of birth as an instrument for identifying the causal effect of schooling on outcomes such as earnings and health. The key assumption in these studies is that people born in different quarters of the year do not differ systematically in their unobserved abilities. This study uses genetic data from the US Health and Retirement Study to analyze the validity of the quarter of birth instrument. We find some evidence that genetic factors influencing education are not randomly distributed over the year. However, these factors only slightly change the effect of quarter of birth on schooling.
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