Book Reviews

Reviews of the following books: Sanford and Springvale, Maine in the Days of Fred Philpot; Alfred Maine: The Shakes and the Village; Sanford and Springvale, Maine: A Backward Glance; A Cluster of Maine Villages: Sanford and Springvale, Acton, Shapleigh and Alfred; Village on the Mousam: Sanford and Springvale, Maine; by Harland H. Eastman. Ties of Common Blood: History of Maine\u27s Northeastern Boundary Dispute with Great Britain by Geraldine Tidd Scott

Book Reviews

Reviews of the following books: Hardliners: A History of the Emery-Waterhouse Company by Edgar Allen Beem and Charles L. Hildreth, Jr.; L.L. Bean: The Making of an American Icon by Leon Gorman; Eminent Mainers: Succinct Biographies of Thousands of Amazing Mainers, Mostly Dead and a Few People from Away Who Have Done Something Useful Within the State Maine; Compiled by Arthur Douglas Stover and Maine: Downeast and Different: An Illustrated History by Neil Rolde; ; The Rangeley and Its Region: The Famous Boat and Lakes of Western Maine by Stephen A. Cole; Voyages: A Maine Franco-American Reader, edited by Nelson Madore and Barry Rodrigu

Homophily and Contagion Are Generically Confounded in Observational Social Network Studies

We 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 their behavior or other measurable responses. We 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 we 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 their choices, even when there is no intrinsic affinity between them. We also suggest some possible constructive responses to these results.Comment: 27 pages, 9 figures. V2: Revised in response to referees. V3: Ditt