IDEAS home Printed from
   My bibliography  Save this article

Homophily and Contagion are Generically Confounded in Observational Social Network Studies


  • Cosma Rohilla Shalizi

    () (Carnegie Mellon University, Pittsburgh, PA, USA)

  • Andrew C. Thomas

    (Carnegie Mellon University, Pittsburgh, PA, USA)


The authors consider processes on social networks that can potentially involve three factors: homophily, or the formation of social ties due to matching individual traits; social contagion, also known as social influence; and the causal effect of an individual's covariates on his or her behavior or other measurable responses. The authors show that generically, all of these are confounded with each other. Distinguishing them from one another requires strong assumptions on the parametrization of the social process or on the adequacy of the covariates used (or both). In particular the authors demonstrate, with simple examples, that asymmetries in regression coefficients cannot identify causal effects and that very simple models of imitation (a form of social contagion) can produce substantial correlations between an individual's enduring traits and his or her choices, even when there is no intrinsic affinity between them. The authors also suggest some possible constructive responses to these results.

Suggested Citation

  • Cosma Rohilla Shalizi & Andrew C. Thomas, 2011. "Homophily and Contagion are Generically Confounded in Observational Social Network Studies," Sociological Methods & Research, , vol. 40(2), pages 211-239, May.
  • Handle: RePEc:sae:somere:v:40:y:2011:i:2:p:211-239

    Download full text from publisher

    File URL:
    Download Restriction: no


    Citations are extracted by the CitEc Project, subscribe to its RSS feed for this item.

    Cited by:

    1. Fortin, Bernard & Yazbeck, Myra, 2015. "Peer effects, fast food consumption and adolescent weight gain," Journal of Health Economics, Elsevier, vol. 42(C), pages 125-138.
    2. Fabio Landini & Natalia Montinari & Paolo Pin & Marco Piovesan, 2014. "Friendship Network in the Classroom: Parents Bias and Peer Effects," Discussion Papers 14-06, University of Copenhagen. Department of Economics.
    3. Jacopo Bonan & Pietro Battiston & Jaimie Bleck & Philippe LeMay-Boucher & Stefano Pareglio & Bassirou Sarr & Massimo Tavoni, 2017. "Social Interaction and Technology Adoption: Experimental Evidence from Improved Cookstoves in Mali," Working Papers 2017.47, Fondazione Eni Enrico Mattei.
    4. Shalizi Cosma Rohilla, 2012. "Comment on "Why and When 'Flawed' Social Network Analyses Still Yield Valid Tests of no Contagion"," Statistics, Politics and Policy, De Gruyter, vol. 3(1), pages 1-5, February.
    5. Susanna Gallani, 2015. "Through the Grapevine: Network Effects on the Design of Executive Compensation Contracts," Harvard Business School Working Papers 16-019, Harvard Business School, revised Dec 2016.
    6. Landini, Fabio & Montinari, Natalia & Pin, Paolo & Piovesan, Marco, 2016. "Friendship network in the classroom: Parents bias on peer effects," Journal of Economic Behavior & Organization, Elsevier, vol. 129(C), pages 56-73.
    7. Videras, Julio & Owen, Ann L. & Conover, Emily & Wu, Stephen, 2012. "The influence of social relationships on pro-environment behaviors," Journal of Environmental Economics and Management, Elsevier, vol. 63(1), pages 35-50.
    8. Zhang, J. & Tong, L. & Lamberson, P.J. & Durazo-Arvizu, R.A. & Luke, A. & Shoham, D.A., 2015. "Leveraging social influence to address overweight and obesity using agent-based models: The role of adolescent social networks," Social Science & Medicine, Elsevier, vol. 125(C), pages 203-213.
    9. Yan, Fuhan & Li, Zhaofeng & Jiang, Yichuan, 2016. "Controllable uncertain opinion diffusion under confidence bound and unpredicted diffusion probability," Physica A: Statistical Mechanics and its Applications, Elsevier, vol. 449(C), pages 85-100.
    10. Lacetera, Nicola & Macis, Mario & Mele, Angelo, 2014. "Viral Altruism? Generosity and Social Contagion in Online Networks," IZA Discussion Papers 8171, Institute for the Study of Labor (IZA).
    11. Jesse Shore & Ethan Bernstein & David Lazer, 2014. "Facts and Figuring: An Experimental Investigation of Network Structure and Performance in Information and Solution Spaces," Harvard Business School Working Papers 14-075, Harvard Business School, revised Jun 2014.
    12. Christa Brelsford & Caterina De Bacco, 2018. "Are `Water Smart Landscapes' Contagious? An epidemic approach on networks to study peer effects," Papers 1801.10516,
    13. Sümeyra Atmaca & Koen Schoors & Marijn Verschelde, 2016. "Bank Loyalty, Social Networks And Crisis," Working Papers of Faculty of Economics and Business Administration, Ghent University, Belgium 16/923, Ghent University, Faculty of Economics and Business Administration.
    14. Aronson, Brian, 2016. "Peer influence as a potential magnifier of ADHD diagnosis," Social Science & Medicine, Elsevier, vol. 168(C), pages 111-119.
    15. Perkins, Jessica M. & Subramanian, S.V. & Christakis, Nicholas A., 2015. "Social networks and health: A systematic review of sociocentric network studies in low- and middle-income countries," Social Science & Medicine, Elsevier, vol. 125(C), pages 60-78.
    16. Ryohei Hisano & Tsutomu Watanabe & Takayuki Mizuno & Takaaki Ohnishi & Didier Sornette, 2015. "The gradual evolution of buyer--seller networks and their role in aggregate fluctuations," Papers 1506.00236,, revised Aug 2016.
    17. Evans, Clare R. & Onnela, Jukka-Pekka & Williams, David R. & Subramanian, S.V., 2016. "Multiple contexts and adolescent body mass index: Schools, neighborhoods, and social networks," Social Science & Medicine, Elsevier, vol. 162(C), pages 21-31.
    18. Daw, Jonathan & Margolis, Rachel & Verdery, Ashton M., 2015. "Siblings, friends, course-mates, club-mates: How adolescent health behavior homophily varies by race, class, gender, and health status," Social Science & Medicine, Elsevier, vol. 125(C), pages 32-39.
    19. Juha Itkonen, 2015. "Social ties and concern for global warming," Climatic Change, Springer, vol. 132(2), pages 173-192, September.
    20. Eesley, Charles & Wang, Yanbo, 2017. "Social influence in career choice: Evidence from a randomized field experiment on entrepreneurial mentorship," Research Policy, Elsevier, vol. 46(3), pages 636-650.
    21. Centola, Damon & van de Rijt, Arnout, 2015. "Choosing your network: Social preferences in an online health community," Social Science & Medicine, Elsevier, vol. 125(C), pages 19-31.


    All material on this site has been provided by the respective publishers and authors. You can help correct errors and omissions. When requesting a correction, please mention this item's handle: RePEc:sae:somere:v:40:y:2011:i:2:p:211-239. See general information about how to correct material in RePEc.

    For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: (SAGE Publications). General contact details of provider: .

    If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

    We have no references for this item. You can help adding them by using this form .

    If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your RePEc Author Service profile, as there may be some citations waiting for confirmation.

    Please note that corrections may take a couple of weeks to filter through the various RePEc services.

    IDEAS is a RePEc service hosted by the Research Division of the Federal Reserve Bank of St. Louis . RePEc uses bibliographic data supplied by the respective publishers.