Thomas S. Dee, a professor of economics at Swarthmore College, has released a statistical study of the impact of gay marriage and civil unions in Europe on the prevalence of sexually transmitted infections.
From the report’s conclusion:
The simple theoretical model introduced here suggests that gay marriage could actually influence STI rates in a number of potentially contradictory ways. However, the empirical evidence presented here is consistent with the view that gay marriage reduces
risky sexual behavior. Specifically, panel-based evaluations using data from European countries suggested that national recognition of same-sex partnerships led to large and statistically significant reductions in syphilis rates of approximately 24 percent. The
estimated effects of gay marriage on gonorrhea and HIV were smaller and statistically insignificant.
These results suggest that gay marriage might reduce, perhaps dramatically, the social costs associated with STI like syphilis. In the United States, over 34,000 cases of 25 syphilis were reported in 2003 (CDC 2004b). And the direct and indirect annual costs of syphilis have been estimated at nearly $1 billion, which reflects in large part, the role that syphilis plays in spreading HIV (CDC 1999). However, the policy relevance of these results probably extends beyond the issue of improvements in public health. For many who are debating the desirability of gay marriage, these results may be more important because of what they suggest about the likely effects of gay marriage on the degree of personal commitment in same-sex relationships.
A PDF copy of the report is available for $5 from the National Bureau of Economic Research.