Genetic Markers as Instrumental Variables: An Application to Child Fat Mass and Academic Achievement
Posted: 6 Jul 2011
Date Written: June 2010
The use of genetic markers as instrumental variables (IV) is receiving increasing attention from economists. This paper examines the conditions that need to be met for genetic variants to be used as instruments. We combine the IV literature with that from genetic epidemiology, with an application to child adiposity (fat mass) and academic performance. We use a direct measure of fat mass (determined by a dual-energy X-ray absorptiometry (DXA) scan), rather than the generally used BMI which incorporates both fat and lean mass. OLS results indicate that leaner children perform slightly better in school tests compared to their more adipose counterparts, but the IV findings show no evidence that fat mass affects academic outcomes.
Keywords: Adiposity, BMI, educational attainment, Fat Mass, Genetic Variant, instrumental variables, Mendelian Randomization
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