3,029 people took part in the study
Martina Björkman Nyqvist, Stockholm School of Economics
Lucia Corno, University of London
Damien De Walque, The World Bank
Jakob Svensson, Stockholm University
by Lesotho's Ministry of Health and Social Welfare
Lesotho has always had a very high rate of HIV/AIDS infection, with an estimated one in four people living with HIV, according to UNAIDS. In 2010, researchers supported by SIEF sought to test whether the chance to win money for staying free of sexually transmitted infections would help reduce risky sexual behavior among young adults and cut the transmission of HIV.
The Lesotho lottery provided the opportunity to people to receive a relatively large cash award if they tested negative for two curable sexually transmitted infections, syphilis and trichonomiasis. Participants were tested every four months and those who were negative qualified for a chance to win a cash award. Participants were divdied into a “low-value” and a “high-value” group. The low-value group could win 500 maloti (USD $50), and the high-value group could win 1000 maloti (USD $100). The high-value award was equivalent to roughly 5.2% of annual earnings for men and 9.1% for women on average.
The study took place in 29 mainly rural villages across five districts in Lesotho. Men and women between the ages of 18 and 32 were eligible to enroll, whether or not they were HIV-positive or HIV-negative. About 40 percent of the age-eligible population in the targeted villages volunteered to participate in the study. People were randomly assigned to either one of the two treatment arms or the control group. While the control group did not qualify for the lottery payments, they otherwise received the testing and services as the treatment group if they tested positive for a sexually transmittable infection. Participants were tested for syphilis and trichomoniasis at baseline and before each lottery draw every four months. Those who tested negative were eligible for the lottery. In total, participants were tested seven times over three years between February 2010 and February 2013. Lottery tickets were given out at five of those test periods, excluding baseline and endline. In addition, participants were tested for HIV at baseline and then after 16 months, 20 months, 24 months, and 36 months, although testing positive for HIV alone did not preclude someone from taking part in the lottery.
The anticipation of winning a lottery payment reduced the HIV incidence, or the number of new infections over the two-year trial period by 2.5 percentage points, or 21.4 percent. The prevelance of HIV infections among the population being studied declined by 3.4 percentage points, or 12.6 percent. Lottery incentives appeared to be particularly effective in targeting individuals who were more prone to risky sexual behavior, which is in line with the hypothesis that lotteries are more valued by individuals willing to take risks.