Internet’s Dirty Secret: Assessing the Impact of Online ...

Internet's Dirty Secret: Assessing the Impact of Online Intermediaries on HIV Transmission

(Accepted at MIS Quarterly)

Jason Chan New York University Stern School of Business 44 West Fourth Street, Suite 8-185 New York, NY 10012

United States jchan@stern.nyu.edu

Anindya Ghose New York University Stern School of Business 44 West Fourth Street, Suite 8-94 New York, NY 10012

United States aghose@stern.nyu.edu

Abstract

Online platforms offer access to a larger social group than is generally available through offline

contacts, making the internet an emerging venue for seeking casual sex partners. The ease of

seeking sex partners through classified ad sites may promote risky behaviors that increase transmission of STDs. In this paper, using a natural experiment set up, we investigate whether

the entry of a major online personals ad site, Craigslist, increases the prevalence of HIV over a 10 year period from 1999 to 2008 across 33 states in the United States. After controlling for

extraneous factors, our results suggest that the entry of Craigslist is related to a 15.9 percent

increase in HIV cases. Our analysis suggests that the site entry produces an average of 6130 to 6455 cases of HIV infection in the U.S. each year, mapping out to $62 million to $65.3 million

in annual treatment costs. In addition, the analyses reveal that non-market related casual sex is

the primary driver of the increase in HIV cases, in contrast to paid transactions solicited on the site (e.g., escort services and prostitution) which has a negative relationship with HIV trends.

These findings are essential to the understanding of the social routes through which HIV transmission takes place and the extent to which site entry can influence HIV trends.

Implications for healthcare practitioners and policy makers are discussed.

Keywords: classified ad sites, HIV, internet, online intermediaries, transmission route

The authors thank Allan Collard-Wexler, Gordon Gao, Avi Goldfarb, Shane Greenstein, Robert Seamans, Rahul Telang Catherine Tucker, and seminar participants at the 2nd Workshop of Health IT and Economics (WHITE 2011), the 2012 International Industrial Organization Conference, the 34th Annual NBER Summer Institute, the 2012 Statistical Challenges in ECommerce Research (SCECR), and the 2013 NET Institute Conference for extremely valuable suggestions. We acknowledge the NET Institute for financial support. The usual disclaimers apply.

Internet's Dirty Secret: Assessing the Impact of Online Intermediaries on HIV Transmission

1. Introduction

Over the last decade, the internet has emerged as a popular platform for seeking sex partners. The expansive reach offered by the internet provides access to a larger social group than is generally available through offline contacts, making it easier for individuals to locate similar others who are seeking casual sex (Garofalo et al. 2007). In particular, the introduction of online classified advertising sites and hook up sites has greatly facilitated the search for casual sex partners. The availability and anonymity in individual browsing coupled with non-costly posting of online ads result in an increased access to potential sex partners and subsequently, a heightened frequency of casual sex encounters (Moskowitz and Seal 2010, Grov 2010). In addition, the convenience brought by online personal ad listings in facilitating casual hook ups produces a shift in individual's casual sex-seeking behavior. Interviews reveal that not only do users search for strangers online to have no-strings attached relationships; they also post ads to solicit more diverse sexual experiences with multiple partners.1,2 A major risk of having casual sex with online strangers involves the possibility of contracting sexually transmitted diseases (STDs). No matter how carefully one tries to vet one's partners, it is typically difficult to accurately know their STD status. Consequently, the increase in casual sex frequency and sexual partners are likely to induce a greater incidence of STDs within the population.

1 For instance, a 32-year old newspaper editor posted an ad in which she declared December 2002 to be a moral free zone, where she would have sex with whoever she wants with minimum self restrain. Her ad received responses from 70 men of which she met up with ten. Report available at . 2 Personal ads are also being used by individuals to look for extramarital affairs as exemplified by the recent case of the married Congressman, Christopher Lee. In an attempt to solicit a woman found on Craigslist's personals section, the Congressman emailed his shirtless photo to her. Lee made an abrupt resignation from his Upstate New York seat when news of his correspondence was reported online. Report available at .

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STDs are a major public health concern that imposes both physical strains and psychological stigmatization on infected patients. Apart from these consequences, STDs impose a heavy economic toll on society: it costs the U.S. healthcare system $16.4 billion to treat 19 million new STD infections each year.3 Among various STDs, the HIV epidemic stands out as an important public health problem that involves widespread mortality and morbidity, and has crucial social and economic consequences (UNAIDS 2009). Tracking the progression of HIV infection and identifying the source of its transmission routes is necessary for effective intervention and treatment of the affected population. As online technology increasingly permeates society and personal lives, its usage warrants closer examination to understand its potential impact on disease transmission. Exogenous technology shocks via the entry of online classified ad sites can disrupt the control over HIV proliferation and undermine the effectiveness of HIV prevention programs. Though the relationship between online classified ads sites and HIV progression bears crucial importance, we have limited understanding on how the increased usage of online classified ad sites affects HIV trends over time (Chiasson et al. 2006, Grov 2010).

This study aims to investigate whether the entry of a major classified ad website, Craigslist, increases the prevalence of HIV cases. Craigslist is a website featuring free online classified ads with sections devoted to jobs, housing, personals, items and services for sale. It was started in 1995 as an email distribution list of friends in San Francisco Bay area. As the service got more popular in 1996, a web interface was established. Following that, Craigslist was incorporated as a company in 1999 and began to expand to other locations. Craigslist expanded steadily over the

3 Figures reported by Center for Disease Control and Prevention on 2

years and is present in more than 700 local sites in 70 countries in 2011.4 A typical personal ad post on Craigslist consists of an open-ended text requesting for meet up, a telephone number, a randomly generated Craigslist email address, and photographs of the poster. Personal ads are classified into subcategories that denote the relationship type that users are seeking for (i.e., men seeking men, men seeking women, women seeking men, women seeking women). Upon closer examination of the content of personal ads, it is observed that numerous ads are posted with the interest of soliciting casual sex partners.

The synchronicity between the presence of Craigslist in a given region and HIV incidence in that region sets the initial motivation to suspect a relationship between the two. Figure 1 illustrates the patterns in HIV incidence and Craigslist's presence in different regions of the United States (U.S.). In the East Central area, the annual number of new HIV cases was relatively stable from 2001 to 2004. An upward trend in HIV incidence is observed in the region as more Craigslist sites were launched post-2005 and is most acute when the number of personal ads increases past the 31,200 mark. In the West Central and Mountain areas, the peaks in HIV prevalence are falling prior to 2002. As the activity levels on Craigslist sites grew after 2003, the peaks in HIV incidence began to rise accordingly.

It is posited that the increase in HIV prevalence results from the entry of Craigslist sites in the country. In particular, we argue that the introduction of Craigslist provides users with the ability to locate and socialize with specific groups of individuals who are inclined to engage in casual sex but are otherwise hard to locate in one's day-to-day life and community. By presenting

4 It is observed that Craigslist does not actively advertise about its entry in new locations. Traffic to the site is driven mainly by word of mouth. See for more information on its entry characteristics, accessed August 2011.

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participants with key information regarding sexual encounters, including (i) location and time of meet up, (ii) physical characteristics of potential partners (e.g., ethnicity, age, physical build, voluptuousness), (iii) societal characteristics (e.g., wealth, job, marital status), (iv) sexual orientation and (v) specific expectations and requests of intimate exchange, personal ads not only signal sexual availability of individuals but also facilitate the matching of casual sex partners.

Figure 1: The relationship between HIV trends and Craigslist entry and activity level

Using a national panel data set constructed from six sources, we examine the longitudinal relationship between Craigslist's entry and HIV trends in 33 U.S. states from 1999 to 2008. To identify the entry effects on HIV proliferation, we rely on a natural experiment setup inherent in Craigslist's expansion in the United States. During its expansion, the classified ad site was made available in certain locations at each time period, thereby providing an exogenous source of variation in site entry across states and years. Exploiting the natural experiment framework, we run panel regressions of HIV incidence on site entry with state and year fixed effects, and included multiple controls to account for demographic features, socioeconomic factors and

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