The Internet’s Dirty Little Secret: New Research from NYU Stern Finds Craigslist Linked to Rise of STDs

NEW YORK--()--The Craigslist website has become synonymous with easily linking up buyers and sellers of products and services in many US states with no monetary cost. According to new research by Anindya Ghose, New York University Stern School of Business Associate Professor of Information, Operations and Management Sciences, with doctoral student Jason Chan, the online classified may provide more than a forum for commerce and camaraderie, and indeed comes with a high cost. The authors find that the expansion of Craigslist into different US states over eight years has increased the incidence of sexually transmitted diseases (STDs) because of the personal ads that enable casual sexual encounters.

The authors constructed a nationwide panel of data, consisting of the rates of new STD cases in 50 states and the District of Columbia (DC) from 1998 to 2005. Among the STDs reported, they focused on AIDS and syphilis. 137 million ads were created in the analysis period, with a mean of 83,878 ads generated in each state per quarter.

Specifically the authors found that:

  • The entry of Craigslist leads to a 14 percent increase in the rate of new AIDS cases, tracking to 6,658 new AIDS infections in the United States each year and resulting in more than $94 million in annual treatment costs.
  • The entry of Craigslist creates an 18.8 percent increase in the rate of new syphilis cases, leading to annual treatment costs of more than $0.84 million.
  • Specific types of personal ads on Craigslist impact the specific types of STDs. The increase in the AIDS rate is influenced by the number of "Men Seeking Men" ads. The increase in the syphilis rate is influenced by both the number of "Men Seeking Women" and "Women Seeking Men" ads.
  • The rise in STD trends caused by Craigslist's entry into a given market is attributed to casual encounters solicited via the site and not market-related sexual transactions such as prostitution or escort service activities.

“Our study results demonstrate that Craigslist, as a minimally regulated online intermediary with no posting costs, increases the number of transactions taking place, including transactions that have undesirable social consequences,” said Professor Ghose. “Despite the known health risks involved, market participants exert little regulation over their casual sex behavior, resulting in more STD infections and a need for more resources to diagnose and treat infected individuals.”

To study the impact of Craigslist's entry, the authors collected data on the months and the states in which new Craigslist sites are launched as well as data from a wide variety of sources including the US Census, the Center for Disease Control (CDC) and the Federal Communications Commission (FCC). In 2000, Craigslist launched in Boston, Chicago, New York and 6 other cities, and the site expanded into four cities during each of the following two years and continued to expand into 14 cities in 2003. As of 2011, Craigslist is present in more than 700 local sites in 70 countries.

Professor Anindya Ghose is an expert in the economic impact of social media, digital marketing, internet commerce and mobile advertising. To read the full paper, “Internet's Dirty Secret: Assessing the Impact of Technology Shocks on the Outbreaks of Sexually Transmitted Diseases,” visit: The paper was awarded the Best Paper Award at the WHITE conference at the University of Maryland.

To arrange an interview with Prof. Ghose, please contact him directly at or contact Rika Nazem in NYU Stern’s Public Affairs Office at or 212-998-0678.


NYU Stern’s Public Affairs Office
Rika Nazem, 212-998-0678

Release Summary

According to new research by Anindya Ghose, the expansion of Craigslist has increased the incidence of STDs because of the personal ads that enable casual sexual encounters.


NYU Stern’s Public Affairs Office
Rika Nazem, 212-998-0678