Exploiting Externalities to Estimate the Long-Term Effects of Early Childhood Deworming

Published in American Economic Journal: Applied Economics, 2018


I investigate whether a school-based deworming intervention in Kenya had long-term effects on young children. I exploit positive externalities from the program to estimate impacts on younger children who were not directly treated. Ten years after the intervention, I find large cognitive effects—comparable to between 0.5 and 0.8 years of schooling—for children who were less than one year old when their communities received school-based mass deworming treatment. I find no effect on child height or stunting. I also estimate effects among children whose older siblings received treatment directly; in this subpopulation, cognition effects are nearly twice as large.

Other versions

Link to published paper in American Economic Journal: Applied Economics

Pre-print 2017 manuscript (pdf)

Earlier version appears as World Bank WPS 7052, October 2014, also available from SSRN


Data and analysis files: (hosted at ICPSR)


Featured in World Bank Development Research e-Newsletter May 2017, Deworming in early childhood can benefit younger siblings and the community

August 2015 VOX article: Mass deworming: (Still) a best buy for international development

July 2015 Center for Global Development blog post discussion: Mapping the Worm Wars: What the Public Should Take Away from the Scientific Debate about Mass Deworming

July 2015 GiveWell blog post discussion: New deworming reanalyses and Cochrane review

Featured in World Bank Development Research e-Newsletter November 2014

October 2014 blog post and video on Africa Can End Poverty: Deworming improves child cognition. Eventually.

Policy brief

September 2015 World Bank Evidence to Policy note: KENYA: Do Infants Benefit When Older Siblings are Dewormed? (also available in French)

Other information

Presentation at ASSA 2017

IPA project page

JEL codes: I10, O12, O15

Recommended citation: Ozier, Owen. "Exploiting externalities to estimate the long-term effects of early childhood deworming." American Economic Journal: Applied Economics 10, no. 3 (2018): 235-62

DOI: https://doi.org/10.1257/app.20160183