Preferential attachment in sexual networks

doi:10.1073/pnas.0611337104

Preferential attachment in sexual networks

^†Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, POB 1122, Blindern, N-0317 Oslo, Norway; and
^‡Departments of Mathematics and
^§Sociology, Stockholm University, S-106 91 Stockholm, Sweden

Edited by H. Eugene Stanley, Boston University, Boston, MA, and approved April 26, 2007 (received for review December 20, 2006)

Abstract

Many social networks are characterized by a highly uneven distribution of links. The observed skewed distributions have in several cases been attributed to preferential attachment (PA), a tendency among nodes in a growing network to form new links preferentially to nodes with high numbers of links. We test the PA conjecture in sexual contact networks. A maximum likelihood estimation-based expectation–maximization fitting technique is used to model new partners over a 1-year period based on the number of partners in foregoing periods of 2 years, 4 years, and lifetime. The PA model is modified to account for individual heterogeneity in the inclination to find new partners and fitted to Norwegian survey data on heterosexual men and women. Results show evidence of nonrandom, sublinear PA when comparing the growth in 3- to 5-year periods. The potential implications of these findings are discussed.

Footnotes

^¶To whom correspondence should be addressed. E-mail: fredrik.liljeros{at}sociology.su.se
Author contributions: B.F.d.B., Å.S., and F.L. designed research; B.F.d.B., Å.S., and F.L. performed research; B.F.d.B. and Å.S. analyzed data; and B.F.d.B., Å.S., and F.L. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0611337104/DC1.
Abbreviations:

pmf,

probability mass function;

PA,

preferential attachment.
Freely available online through the PNAS open access option.