Identification of Homophily and Preferential Recruitment in Respondent-Driven Sampling

Abstract

Respondent-driven sampling (RDS) is a link-tracing procedure used in epidemiologic research on hidden or hard-to-reach populations in which subjects recruit others via their social networks. Estimates from RDS studies may have poor statistical properties due to statistical dependence in sampled subjects' traits. Two distinct mechanisms account for dependence in an RDS study: homophily, the tendency for individuals to share social ties with others exhibiting similar characteristics, and preferential recruitment, in which recruiters do not recruit uniformly at random from their network alters. The different effects of network homophily and preferential recruitment in RDS studies have been a source of confusion and controversy in methodological and empirical research in epidemiology. In this work, we gave formal definitions of homophily and preferential recruitment and showed that neither is identified in typical RDS studies. We derived nonparametric identification regions for homophily and preferential recruitment and showed that these parameters were not identified unless the network took a degenerate form. The results indicated that claims of homophily or recruitment bias measured from empirical RDS studies may not be credible. We applied our identification results to a study involving both a network census and RDS on a population of injection drug users in Hartford, Connecticut (2012-2013).

Estimation and correction of bias in network simulations based on respondent-driven sampling data

“…If there were more coupons left than the number of partners (s)he had, the extra coupons were discarded. The probability of recruiting each partner could be equal (non-preferential recruitment) or based on preferential recruitment of partners sharing the same gender 37 . Among the 5000 RDS simulations used to examine homophily, 1000 assumed non-preferential recruitments and 4000 assumed preferential recruitment.…”

Update on respondent-driven sampling: Theory and practical considerations for studies of persons who inject drugs

“…Thus, if the focus is on drug users and if a user knows n users in his or her social network, he or she will be considered to have a degree equal to n. There is probably a difference between the true degree and the reported degree, noted d i  . When an individual tends to recruit persons who resemble him or her, especially with regard to the variable of interest, this is classically defined as homophily, even if several definitions coexist (Crawford et al, 2015;Tyldum and Johnston, 2014). Homophily will be high (1.0) if the infected persons (or non-infected persons, as the case may be) recruit only other infected (or non-infected) persons.…”

Social Network Clustering and the Spread of HIV/AIDS Among Persons Who Inject Drugs in 2 Cities in the Philippines

“…For instance, RDS asks each respondent about his personal network size. Some RDS surveys also examine the extent to which respondents resemble their recruiters [27,28], which is similar to the notion of homophily in sociology [29], though this practice is controversial [30]. …”