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Is obesity contagious? Social networks vs. environmental factors in the obesity epidemic

  • Cohen-Cole, Ethan
  • Fletcher, Jason M.

This note's aim is to investigate the sensitivity of Christakis and Fowler's claim [Christakis, N., Fowler, J., 2007. The spread of obesity in a large social network over 32 years. The New England Journal of Medicine 357, 370-379] that obesity has spread through social networks. It is well known in the economics literature that failure to include contextual effects can lead to spurious inference on "social network effects." We replicate the NEJM results using their specification and a complementary dataset. We find that point estimates of the "social network effect" are reduced and become statistically indistinguishable from zero once standard econometric techniques are implemented. We further note the presence of estimation bias resulting from use of an incorrectly specified dynamic model.

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Article provided by Elsevier in its journal Journal of Health Economics.

Volume (Year): 27 (2008)
Issue (Month): 5 (September)
Pages: 1382-1387

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Handle: RePEc:eee:jhecon:v:27:y:2008:i:5:p:1382-1387
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  1. Durlauf,S.N., 2003. "Neighborhood effects," Working papers 17, Wisconsin Madison - Social Systems.
  2. Lee, Lung-fei, 2007. "Identification and estimation of econometric models with group interactions, contextual factors and fixed effects," Journal of Econometrics, Elsevier, vol. 140(2), pages 333-374, October.
  3. David M. Cutler & Edward L. Glaeser & Jesse M. Shapiro, 2003. "Why Have Americans Become More Obese?," Harvard Institute of Economic Research Working Papers 1994, Harvard - Institute of Economic Research.
  4. Charles F. Manski, 1993. "Identification of Endogenous Social Effects: The Reflection Problem," Review of Economic Studies, Oxford University Press, vol. 60(3), pages 531-542.
  5. Bramoullé, Yann & Djebbari, Habiba & Fortin, Bernard, 2009. "Identification of peer effects through social networks," Journal of Econometrics, Elsevier, vol. 150(1), pages 41-55, May.
  6. Krauth, Brian V., 2006. "Simulation-based estimation of peer effects," Journal of Econometrics, Elsevier, vol. 133(1), pages 243-271, July.
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