The Impact of Positive Income Shocks on Risky Sexual Behavior: Experimental Evidence from Tanzania


In this paper, we exploit a lottery in Tanzania, which randomly assigned eligible participants to receive $100 cash grants. The randomized nature of the lottery allows us to estimate the causal impact of positive income shocks on risky sexual behavior. We found that winning the lottery led men to have 0.28 (95 % CI 0.14, 0.55) more sexual partners and to a 0.21 (95 % CI 0.01–0.4) increase in the probability of unprotected sex with a non-primary partner relative to a control group of eligible non-winners. We found no significant effect of winning the lottery on the sexual behavior of women.

This is a preview of subscription content, access via your institution.

Fig. 1


  1. 1.

    Institute for Health Metrics and Evaluation (IHME). GBD Heatmap. Seattle, WA: IHME, University of Washington, 2013. Accessed 8 March 2015.

  2. 2.

    Chen L, Jha P, Stirling B, et al. Sexual risk factors for HIV infection in early and advanced HIV epidemics in Sub-Saharan Africa: systematic overview of 68 epidemiological studies. PLoS One. 2007;2(10):e1001.

    Article  PubMed  PubMed Central  Google Scholar 

  3. 3.

    Burke M, Gong E, Jones K. Income shocks and HIV in Africa. Econ J. 2014;125:1157–89.

    Article  Google Scholar 

  4. 4.

    Baird SJ, Garfein RS, McIntosh CT, Özler B. Effect of a cash transfer programme for schooling on prevalence of HIV and herpes simplex type 2 in Malawi: a cluster randomised trial. Lancet. 2012;379(9823):1320–9.

    Article  PubMed  Google Scholar 

  5. 5.

    Kohler H-P, Thornton RL. Conditional cash transfers and HIV/AIDS prevention: unconditionally promising? World Bank Econ Rev. 2011;26:165–90.

    Article  Google Scholar 

  6. 6.

    de Walque D, Dow WH, Gong E. Coping with risk: the effects of shocks on reproductive health and transactional sex in rural Tanzania. Unpublished 2013.

  7. 7.

    DHS implementing partners and ICF International. Demographic and Health Surveys 2003–2011 [Dataset, modify years as appropriate]. Data extract from DHS Recode files. IPUMS-Demographic and Health Surveys (IPUMS-DHS), version 3.0, Minnesota Population Center and ICF International [Distributors].

  8. 8.

    Glynn JR, Caraël M, Auvert B, et al. Why do young women have a much higher prevalence of HIV than young men? A study in Kisumu, Kenya and Ndola. Zamb Aids. 2001;15:S51–60.

    Article  Google Scholar 

  9. 9.

    Gertler P, Shah M, Bertozzi SM. Risky business: the market for unprotected commercial sex. J Polit Econ. 2005;113(3):518–50.

    Article  Google Scholar 

  10. 10.

    Garcia M, Moore CG, Moore CM. The cash dividend: the rise of cash transfer programs in sub-Saharan Africa. Washington: World Bank Publications; 2012.

    Book  Google Scholar 

  11. 11.

    Björkman-Nyqvist M, de Walque D, Corno L, Svensson J. Using lotteries to incentivize safer sexual behavior: evidence from a randomized controlled trial on HIV prevention. Washington: World Bank Policy Research Working Paper; 2015.

    Book  Google Scholar 

  12. 12.

    Gong E. HIV testing and risky sexual behaviour. Econ J. 2014;125:32–60.

    Article  Google Scholar 

Download references


The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent.


We gratefully acknowledge funding by the World Bank Research Committee, the Strategic Impact Evaluation Fund (SIEF), the Bank-Netherlands Partnership Program (BNPP), Trust Fund for Environmentally & Socially Sustainable Development (TFESSD) and Knowledge for Change Program (KCP) managed by the World Bank, and the William and Flora Hewlett Foundation through the Population Reference Bureau and the National Institute on Aging (Grant #T32-AG000246).

Author information



Corresponding author

Correspondence to Zachary Wagner.

Ethics declarations

Conflict of Interest

All authors have no conflicts of interest to declare.

Ethical Approval

The study protocol was initially approved by the University of California, Berkeley’s Institutional Review Board and Tanzania’s National Institute for Medical Research. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

Informed consent was obtained from all individual participants included in the study.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (DOCX 149 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Wagner, Z., Gong, E., de Walque, D. et al. The Impact of Positive Income Shocks on Risky Sexual Behavior: Experimental Evidence from Tanzania. AIDS Behav 21, 650–654 (2017).

Download citation


  • Lottery
  • Risky sexual behavior
  • Tanzania
  • Income shocks