Health Certification in Sex Markets: A Field Experiment in Dakar, Senegal

Last registered on August 19, 2021


Trial Information

General Information

Health Certification in Sex Markets: A Field Experiment in Dakar, Senegal
Initial registration date
August 16, 2021

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
August 19, 2021, 10:53 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.



Primary Investigator

Washington State University

Other Primary Investigator(s)

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial is based on or builds upon one or more prior RCTs.
A common approach to sex work regulation is "legalization and regulation," which aims to reduce infectious disease by providing government certification of female sex workers’ health. In markets where suppliers possess important, unobservable information, theory predicts that credible certification can improve welfare. However, in a sample of uncertified female sex workers, take-up of a randomly offered incentive to obtain certification was only 7%. The results suggest that there is no price premium for certification, and that internalized stigma deters women from seeking certification. Complementary services for uncertified sex workers may be needed to achieve sexually transmitted infection control.
External Link(s)

Registration Citation

Manian, Shanthi. 2021. "Health Certification in Sex Markets: A Field Experiment in Dakar, Senegal." AEA RCT Registry. August 19.
Experimental Details


Senegal has had a female sex worker certification program since 1969. In a sample of uncertified female sex workers, an encouragement intervention was delivered to members of the treatment group. The encouragement intervention involved two parts. First, the treatment group participated in a 30-minute persuasive discussion with the peer educators, who were certified sex workers. The second part of the encouragement was a cash certification incentive. We offered a total of 6,000 FCFA to anyone who got certified within 15 days. This amount was designed to provide reimbursement of the 1,000 FCFA clinic visit fee and 5,000 FCFA to the sex worker. In order to claim the incentive, participants had to return to the study offices and show their certification card to study staff.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Transaction price
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
I implemented the study in partnership with a community-based organization, Association AWA, that provides services to certified and uncertified sex workers. From October 2015 to February 2016, participants were recruited using respondent-driven sampling, a peer-referral recruitment method that is frequently used for hidden populations such as sex workers. Thirty one "seeds" were purposively selected among sex workers currently participating in HIV prevention projects with AWA. These seeds were then asked to recruit three sex workers meeting eligibility criteria for the study. Those recruited were, in turn, be asked to recruit three more sex workers. Recruitment continued through this peer referral until the target sample size was obtained.

In total, from October 2015 to February 2016, we recruited and conducted baseline surveys for 400 female sex workers. Of these, 314 participants were eligible and randomized to a treatment group, which received an encouragement intervention, or a control group. Between December 2015 and June 2016, 291 participants completed endline surveys, representing a 93 percent retention rate from randomization to follow-up.
Experimental Design Details
Randomization Method
Public lottery, conducted over multiple randomization sessions.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
291, after attrition
Sample size (or number of clusters) by treatment arms
164 treatment, 151 control
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)


Post Trial Information

Study Withdrawal

There is information in this trial unavailable to the public. Use the button below to request access.

Request Information


Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials