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Safe Sex for a Chance to Win: Evidence from a field experiment on HIV Prevention
Last registered on December 05, 2014

Pre-Trial

Trial Information
General Information
Title
Safe Sex for a Chance to Win: Evidence from a field experiment on HIV Prevention
RCT ID
AEARCTR-0000567
Initial registration date
December 05, 2014
Last updated
December 05, 2014 9:53 AM EST
Location(s)
Region
Primary Investigator
Affiliation
Stockholm School of Economics
Other Primary Investigator(s)
PI Affiliation
The World Bank, Development Research Group
PI Affiliation
IIES, Stockholm University
PI Affiliation
Queen Mary, University of London
Additional Trial Information
Status
Completed
Start date
2010-01-01
End date
2013-05-01
Secondary IDs
Abstract
How to stimulate demand for HIV prevention at relatively low costs and how to target those at high risk of getting infected by the disease are common concerns in most HIV prevention programs. We present evidence from a two-year field experiment in which individuals were offered relatively low monetary incentives (in expectations) conditional on testing negative for two curable sexually transmitted infections (STIs), but where the transfer were given in the form of a lottery ticket with a chance of winning a high price. The intervention resulted in a large reduction in HIV incidence and prevalence in the treatment as compared to the control group. Lottery incentives appear to be particularly effective in targeting individuals with ex ante risky sexual behavior, consistent with the hypothesis that lotteries are more valued by risk-willing individuals and these individuals are also more likely to engage in risky sex.
External Link(s)
Registration Citation
Citation
Björkman Nyqvist, Martina et al. 2014. "Safe Sex for a Chance to Win: Evidence from a field experiment on HIV Prevention." AEA RCT Registry. December 05. https://doi.org/10.1257/rct.567-1.0.
Former Citation
Björkman Nyqvist, Martina et al. 2014. "Safe Sex for a Chance to Win: Evidence from a field experiment on HIV Prevention." AEA RCT Registry. December 05. https://www.socialscienceregistry.org/trials/567/history/3196.
Experimental Details
Interventions
Intervention(s)
Intervention Start Date
2010-02-01
Intervention End Date
2012-06-01
Primary Outcomes
Primary Outcomes (end points)
HIV prevalence and incidence; STI prevalence; sexual behaviour
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
Randomized controlled trial at the individual level in 29 rural and peri-urban villages in 5 out of 10 districts in Lesotho, randomly selected from the 2006 Census. The intervention arm was divided into two sub-arms: A low-value lottery incentive arm eligible to win lottery prizes worth 500 Malotis, or approximately US$50 every four months and a high-value lottery incentive arm with prizes worth 1000 Malotis, or approximately US$100 every four months. The random assignment into the three study arms took place after the baseline interview and STI testing. The randomization was conducted in a transparent way whereby each participant were asked to draw a marble from an opaque bag that contained 10 marbles: 4 marbles assigning to the control arm, 3 marbles assigning to the low lottery prize arm and 3 marbles assigning to the high lottery prize arm. Final sample of 3,029 individuals in total, where 1,821 individuals were assigned to the two treatment groups and 1,208 individuals were assigned to the control group.
Experimental Design Details
Randomization Method
Randomization done in public through drawing a marble from an opaque bag containing 10 marbles.
Randomization Unit
Individual
Was the treatment clustered?
No
Experiment Characteristics
Sample size: planned number of clusters
Randomized controlled trial at the individual level in 29 rural and peri-urban villages in 5 out of 10 districts in Lesotho.
Sample size: planned number of observations
3029
Sample size (or number of clusters) by treatment arms
The final sample of 3,029 individuals was randomly divided into three groups: 1,208 individuals were assigned to the control group, 962 to the high reward lottery arm and 859 to the low reward lottery arm.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
Ministry of Health and Social Welfare, Lesotho
IRB Approval Date
2009-08-26
IRB Approval Number
18/09
IRB Name
Independent Ethics Committee of the Fondazione Istitutio Nazionale Tumori (IRCCS), Milano, Italy
IRB Approval Date
2009-07-06
IRB Approval Number
D201464
Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
No
Is data collection complete?
Data Publication
Data Publication
Is public data available?
No
Program Files
Program Files
Reports and Papers
Preliminary Reports
Relevant Papers