Cruising for sex on Craigslist personal ads resulted in a 15.9 percent increase in HIV infections after the website entered various U.S. markets, according to a study by the University of Minnesota published in MIS Quarterly.

The study estimates that the Craigslist effect led to about 6,000 additional HIV cases a year from 1999 to 2008 in the 33 states studied, and additional treatment costs of $62 million to $65.3 million.

Jason Chan, an assistant professor of information and decision sciences at the university’s Carlson School of Management, said he got the idea for the study several years ago while working on his doctorate in management-information systems at New York University. Chan’s dissertation focused on the social and health effects of Internet platforms. In the course of his studies, he read about a doctor who traced sexually transmitted diseases to online chat rooms.

“I went to Craigslist in New York and went through the ads. To my shock, I found out almost all the ads were hookup ads. They were very explicit,” said Chan, who wrote the journal article with professor Anindya Ghose of NYU’s Stern School of Business.

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