Lotteries to Incentivize HIV Prevention in Lesotho

Updated: Feb 11, 2020
Evidence Rating:
Near Top Tier


  • Program:

    Village-level lotteries in Lesotho, a small country in southern Africa, conducted every four months for two years to incentivize prevention of HIV and other sexually-transmitted infections (STIs). Village residents could participate in a lottery if they tested negative for two curable STIs – syphilis and trichonomiasis – prior to the lottery. The lotteries offered potential cash prizes of either $50 or $100. The lottery payout averaged $29 per program participant over two years, making this a very inexpensive program.

  • Evaluation Methods:

    A well-conducted randomized controlled trial (RCT) [1] with a sample of 3,029 individuals aged 18-32 years old in Lesotho.

  • Key Findings:

    Three years after random assignment – i.e., one year after the lotteries ended – the program reduced (i) the rate of new HIV infections from 17.1% in the control group to 14.2% in the treatment group (p<0.05), and (ii) infection rates for the two other STIs from 6.5% in the control group to 3.4% in the treatment group (p<0.05).

  • Other:

    The study was conducted in one small country. As a next step in the research, a replication RCT in another country would be desirable to hopefully confirm the initial results and establish that they generalize to other nations with high rates of HIV infection.

Arnold Ventures’ Evidence-Based Policy team continuously monitors and reviews the evaluation literature in international development, as we do in domestic U.S. social policy, to identify programs with credible RCT evidence of important effects on people’s lives. However, given our organization’s focus on U.S. social policy, we only provide “highlights” of our evidence reviews for most international development programs (as shown above), without the accompanying detailed PDF summaries that we provide for U.S. programs.


[1] For example, the study had successful random assignment (as evidenced by highly similar treatment and control groups), minimal sample attrition, and valid outcome measures (biological testing for HIV and other STIs).

Bjorkman Nyqvist, M., Corno, L., De Walque, D., & Svensson, J. (March 2015). “Using lotteries to incentivize safer sexual behavior: Evidence from a randomized controlled trial on HIV prevention.” World Bank Policy Research Working Paper 7215.