Sex Work Regulation and Sexually Transmitted Infections in Tijuana, Mexico

Reducing the transmission of sexually transmitted infections (STIs) is a common argument for regulating sex work. However, only two previous studies have empirically addressed this issue. Gertler and Shah (2011) find that increasing licensing enforcement in the street sector in Ecuador leads to decreases in STI prevalence rates among sex workers, while higher enforcement in the brothel sector increases the probability that a sex worker ever acquires an STI. In their analysis of an unexpected decriminalization of indoor prostitution in Rhode Island, Cunningham and Shah (2014) find that the incidence rate of gonorrhea among the general population fell by 39%. 

We investigate the effects of highly publicized (Spagat 2005, McKinley Jr. 2005) sex work regulations introduced in 2005 in Tijuana, Mexico on the incidence of trichomoniasis. We study Tijuana because of its large sex work industry and concentrate our analysis on trichomoniasis because of its high incidence rate. State-level, annual data for the 1995-2012 period are employed that include the incidence rates of trichomionasis by age group. Variables that reflect the supply of health care and demographic characteristics are used as controls. To estimate the causal effects of the regulation we employ the synthetic control method (Abadie et al, 2010), in which a composite optimal control group (i.e., synthetic state) is created from donor states that most closely match Baja California’s characteristics and trends prior to regulation. 

We find that the regulations led to a decrease in the incidence rate of trichomoniasis. Specifically, in the 2005-2012 period the all-ages incidence rate is roughly 37% lower than what is predicted by our synthetic control estimates and corresponds to approximately 800 fewer reported cases of trichomoniasis per year. We find that the decreases are especially pronounced for 15-24 and 25-44 age cohorts. Further, our diagnostic and placebo tests indicate that our findings are robust to various falsification tests. 

Our results suggest that there may be significant benefits in lowering the rates of STIs from regulating commercial sex. Moreover, our results are consistent with Gertler and Shah's (2011) findings of decreased prevalence rates among sex workers. Thus, while there are many considerations to such policies, the regulation of commercial sex may lead to improved public health.