Vertical Pay Differentials and Worker Productivity: Evidence from the Health Worker Program in Sierra Leone

Last registered on March 10, 2019


Trial Information

General Information

Vertical Pay Differentials and Worker Productivity: Evidence from the Health Worker Program in Sierra Leone
Initial registration date
March 09, 2019

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
March 10, 2019, 10:37 PM EDT

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



Primary Investigator

Northwestern University

Other Primary Investigator(s)

PI Affiliation
University of Pompeu Fabra
PI Affiliation
University of Pompeu Fabra

Additional Trial Information

On going
Start date
End date
Secondary IDs
We test the effect a steeper wage progression between low-tier employees (e.g., frontline service providers) and higher-tier employees (e.g. supervisors, bosses) on organizational performance, and investigate whether this effect differs in more vs. less- meritocratic promotion systems. While steep wage progression may incentivize lower-tier workers to perform better in a meritocratic regime (through career incentives), it may instead demotivate workers in a non-meritocratic regime (through fairness or inequality concerns).

We collaborate with a national public organization—the Community Health Worker Program in Sierra Leone—in which supervisors (high-tier workers) are in charge of monitoring and advising about 9 health workers each (lower-tier workers). Each time a supervisor leaves her position, one of the 9 health workers located in that “health unit” (henceforth, PHU) is promoted to the supervisor position.

Our project takes places in 372 PHUs across 6 districts of Sierra Leone. It introduces exogenous variation at the PHU level on: (1) the perceived gap between health workers’ and supervisors’ earnings (higher vs. lower perceived wage progression), and (2) the extent to which the promotion process is meritocratic or not (higher vs. lower meritocracy).

Our goal is twofold. First, we aim to test the differential effect of increasing the perceived vertical wage steepness in regimes that are more vs. less meritocratic. In particular, we are interested in understanding whether a larger vertical pay gap can motivate workers in meritocratic regimes while demotivate workers in non-meritocratic regimes. Second, we aim to test the effect of meritocratic promotions per se on worker performance, and the heterogonous effect by worker type (ability, social connections, etc.).
External Link(s)

Registration Citation

DESERRANNO, ERIKA, Philipp Kastrau and Gianmarco Leon. 2019. "Vertical Pay Differentials and Worker Productivity: Evidence from the Health Worker Program in Sierra Leone." AEA RCT Registry. March 10.
Former Citation
DESERRANNO, ERIKA, Philipp Kastrau and Gianmarco Leon. 2019. "Vertical Pay Differentials and Worker Productivity: Evidence from the Health Worker Program in Sierra Leone." AEA RCT Registry. March 10.
Experimental Details


This study takes place in the context of the Community Health Worker Program in Sierra Leone. The health program is structured around PHUs, each composed of one peer supervisors (PS) and an average of 9 community health workers (CHW) per PS. CHWs are the frontline workers: they are in charge of visiting households in their villages and provide basic health services: inform them about health, treat/diagnose diseases (whenever possible) and provide ante- or post-natal services. Each CHW is trained, supervised and advised by the peer supervisor (PS) in their corresponding health unit. All CHWs and PSs are entitled to a total monthly compensation of, respectively, SLL 150,000 and SLL 250,000, by the Ministry of Health and Sanitation (MOHS). [$1.00 = SLL 8,450.00] When a supervisor decides to quit her position, one of the 9 health workers she supervises is promoted to the supervisor position.

Until mid-2018, promotions from CHW to PS position were made at the discretion of the head of each PHU and therefore mostly based on personal connections, rather than merit. Starting then, the District Health Officials have committed — in a random half of the 372 PHUs — to use objective performance information as the main input for their promotion decisions (“Meritocracy Treatment”). Performance will be measured through a reporting system that exists in all PHUs. All CHWs in the Meritocracy Treatment are informed about the new promotion system, while CHWs who are not assigned to the Meritocracy Treatment are reminded of the current promotion system.

The experiment further creates random variation at the PHU level in perceived wage steepness. In a random half of the PHUs (stratified by the Meritocracy Treatment), CHWs are informed about the wage gap between their own salary and the supervisor’s salary (Wage Gap Treatment), which they underestimate at baseline. In the other half of the PHUs, CHWs are not informed about the wage gap. We will quantify the effect of the Wage Gap information treatment on the exact increase in CHWs' perceived wage gap through a survey. (More details below).
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Our main outcome variables are measures of CHW beliefs, measures of CHW effort as well as health outcomes of the population. These outcome variables will be obtained from three sources:
1. Baseline and endline CHW surveys -- These surveys will provide us information on worker perception on meritocracy and pay steepness. This will allow us to estimate whether CHWs update their beliefs on meritocracy and wage gap, in which direction they do so and with which intensity. We will also collect information on perceived differences between PS and CHW in terms of hours worked, work-related expenses (transportation and communication), difficulty of the job; and measure in details how strongly CHWs want to get promoted; how they assess their chances to get promoted relative to their peers; how they assess their performance/social connections and their self-reported number of hours of work.
2. Endline household survey of a randomly selected sample of households -- This survey will provide us information on CHW effort (the number of services the household received from the CHW, client satisfaction survey) but also information on households’ health outcomes and health knowledge/behavior.
3. Text message reports of patient services sent by CHWs -- We collect further information on the number of services provided by each CHW through a reporting system which was already in place before we started the experiment. The reporting system works in 2 steps: reporting and monitoring. (1) Reporting: each time a CHW provides a service to a patient, she is asked to send a text message with the name and contact number of the patient to a toll-free number, along with the type of service provided. The information is automatically uploaded to a server and provides a live database of CHW activity. (2) Monitoring: To minimize over or under-reporting, the information provided by the CHWs is double checked by a monitoring team, composed of phone operators and monitors in the field, who call/visit a random subsample of the population and make sure CHWs are neither over- nor under-reporting. The monitors also record the duration of the service (as a proxy for service quality). Each CHW is entitled a fixed bonus of SLL 10,000 conditional on truthful reporting.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
All CHWs in 372 PHUs are randomly assigned to one in four groups of equal size (with randomization at PHU level):
(1) Control Group
(2) Meritocracy Treatment only
(3) Wage Gap Treatment only
(4) Meritocracy Treatment + Wage Gap Treatment
Experimental Design Details
Randomization Method
The randomization was done by a computer using Stata.
Randomization Unit
The unit of randomization is the PHU (n=372).
Randomization was stratified by district. This is because we expect districts to strongly affect our main outcomes variables (e.g., CHW performance). Firstly, many operations of the CHW program are decentralized and many decisions are taken at the district level. Secondly, unexpected disease outbreaks or economic and political shocks, which might occur within the study period, could affect outcome variables and would likely vary substantially across districts. Thirdly, districts differ in terms of population density and therefore in terms of the the number of potential patients per CHW; which could affect CHW performance.
This study takes place in the same context as another experiment. We will thus also stratify by the treatment status of this other experiment.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
372 PHUs
Sample size: planned number of observations
We plan to target 2000 CHWs for the CHW surveys and 5 households per CHW for the endline household survey (~15,000 households in total). To be confirmed.
Sample size (or number of clusters) by treatment arms
The 372 PHUs are equally divided in 4 groups: Control Group, Meritocracy Treatment only, Wage Gap Treatment only, Meritocracy + Wage Gap Treatments.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Universitat Pompeu Fabra, CIREP: Institutional Commission for Ethical Review of Projects
IRB Approval Date
IRB Approval Number


Post Trial Information

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