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In addition to (1) peer influence or social contagion and (2) homophily,
isn't there also a rather substantial factor of (3) structural equivalence,
separate from either peer influence or homophily, to consider as a factor in
the adoption of new practices? 

Blyden Potts



-----Original Message-----
From: Social Networks Discussion Forum [mailto:[log in to unmask]] On
Behalf Of Sinan Aral
Sent: Tuesday, January 26, 2010 5:17 PM
To: [log in to unmask]
Subject: Distinguishing Influence and Homophily

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Dear All,

Several on this list may be interesting in this paper we just published in
PNAS. It develops a method for distinguishing peer influence from homophily
in large dynamic networks. We apply it to 27 million users of 
Yahoo's instant messaging graph to predict influence in the adoption of a
new mobile service application. Enjoy:)

http://www.pnas.org/content/106/51/21544.short

"Distinguishing Influence Based Contagion from Homophily Driven Diffusion in
Dynamic Networks"

ABSTRACT:

Node characteristics and behaviors are often correlated with the structure
of social networks over time. While evidence of this type of assortative
mixing and temporal clustering of behaviors among linked nodes is used to
support claims of peer influence and social contagion in networks, homophily
may also explain such evidence. 

Here we develop a dynamic matched sample estimation framework to distinguish
influence and homophily effects in dynamic networks, and we apply this
framework to a global instant messaging network of 27.4 million users, using
data on the day-by-day adoption of a mobile service application and users'
longitudinal behavioral, demographic, and geographic data. 

We find that previous methods overestimate peer influence in product
adoption decisions in this network by 300-700%,
and that homophily explains 50% of the perceived behavioral contagion. These
findings and methods are essential to both our understanding of the
mechanisms that drive contagions in networks and our knowledge of how to
propagate or combat them in domains as diverse as epidemiology, marketing,
development economics, and public health.


-- 
Sinan Aral
Assistant Professor, NYU Stern School of Business.
Research Affiliate, MIT Sloan School of Management.
Personal Webpage: http://pages.stern.nyu.edu/~saral
SSRN Page: http://ssrn.com/author=110270
WIN Workshop: http://www.winworkshop.net

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