Average and quantile treatment effects of the American Folic Acid Fortification: an evaluation in a quasi-experimental framework
The American program of folic acid fortification is generally thought to have increased the average amount of serum folate in the population and, hence, widely considered as a successful public health intervention. We use several waves of the â€œNational Health and Nutrition Examination Surveyâ€ (NHANES) to evaluate the causal impact of the fortification of ready-to-eat cereals on serum folate concentration, using a quasi experimental framework. First, we compute the average treatment effect by using matching methods to solve the problem of selection on observables, finding a strong selection into treatment mainly based on race-ethnicity and education. Second, we assess the distributional impact of the fortification by computing quantile treatment effects, under different assumptions on the dependence between the distributions of potential outcomes, and we find significant variation in the impact of fortification across the population, thus rejecting the common effects model. Fortification appears to have had the least (though still modestly beneficial) impact among those that most needed it and the biggest impact among those that needed it least, thus suggesting the presence of folate over-consumption in the latter group, with potential adverse health effects. Third, by controlling our estimates for the concentration of beta-carotene, we find support for the hypothesis that part of the increase in serum folate concentration can be explained by changes in diet, leaving a smaller attributable effect to the fortification itself.
|Date of creation:||May 2012|
|Date of revision:|
|Contact details of provider:|| Postal: HEDG/HERC, Department of Economics and Related Studies, University of York, York, YO10 5DD, United Kingdom|
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Web page: http://www.york.ac.uk/economics/postgrad/herc/hedg/
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- Marianne Bitler & Jonah Gelbach & Hilary Hoynes, 2003.
"What Mean Impacts Miss: Distributional Effects of Welfare Reform Experiments,"
NBER Working Papers
10121, National Bureau of Economic Research, Inc.
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- Bitler, Marianne P. & Gelbach, Jonah B. & Hoynes, Hilary W., 2005. "What Mean Impacts Miss: Distributional Effects of Welfare Reform Experiments," IZA Discussion Papers 1728, Institute for the Study of Labor (IZA).
- Marianne P. Bitler & Jonah B. Gelbach & Hilary W. Hoynes, 2003. "What Mean Impacts Miss: Distributional Effects of Welfare Reform Experiments," Working Papers 109, RAND Corporation.
- Hilary W. Hoynes & Marianne P Bitler & Jonah Gelbach, 2005. "What Mean Impacts Miss:Distributional Effects of Welfare Reform Experiments," Working Papers 531, University of California, Davis, Department of Economics.
- Markus Frolich & Blaise Melly, 2010. "Estimation of quantile treatment effects with Stata," Stata Journal, StataCorp LP, vol. 10(3), pages 423-457, September.
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