Can Discounted Withdrawal Fees Catalyse Mobile Money Usage? Field Experimental Evidence from Gambia

Last registered on October 12, 2018


Trial Information

General Information

Can Discounted Withdrawal Fees Catalyse Mobile Money Usage? Field Experimental Evidence from Gambia
Initial registration date
October 02, 2018

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
October 03, 2018, 2:07 PM EDT

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

Last updated
October 12, 2018, 5:13 PM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

University of The Gambia

Other Primary Investigator(s)

Additional Trial Information

In development
Start date
End date
Secondary IDs
PIERI 20165
Digital financial products like mobile money are becoming ubiquitous in developing countries. Due to low access to financial services and high access to mobile phones, offering of financial services via mobile phones is heralded as an important tool that can revolutionize financial services adoption and usage in developing countries thereby fostering rapid financial inclusion. However, despite becoming rampant in many developing countries, the role of mobile money in revolutionizing formal financial account access and usage has so far been modest. One reason for this is that marginal costs of the services, such as transaction cost, remain high; in fact, in some cases, the cost are even higher than what commercial banks asked for similar services. Thus, such high cost can limit the attractiveness of digital products like mobile money. Therefore, in this project, we study whether subsidizing cash out fees could stimulate more adoption and usage of mobile services. In other words, we study the responsiveness of usage of mobile money services to changes in price of cash-out fees. To this effect, we use a randomized field experiment where we randomly vary the cost of cash-out charges among some randomly selected clients of a private mobile money service provider in Gambia called Qodoo. The clients are randomly assigned to one of three different withdrawals fees discount: 0%, 15% and 30%. We then study how the adoption of the new offer and usage of their mobile money accounts varies across different withdrawal or cash-out fees subsidies. Thus, by experimentally varying one element of transaction fee (cash-out fees) we can determine how this is relevant for usage rates.

Registration Citation

Jawara, Hamidou. 2018. "Can Discounted Withdrawal Fees Catalyse Mobile Money Usage? Field Experimental Evidence from Gambia." AEA RCT Registry. October 12.
Former Citation
Jawara, Hamidou. 2018. "Can Discounted Withdrawal Fees Catalyse Mobile Money Usage? Field Experimental Evidence from Gambia." AEA RCT Registry. October 12.
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Experimental Details


Our trial target inactive clients of a mobile money service provider in Gambia. inactivity is determined by whether a client uses an account regularly or not. Specifically, we target clients that have not made any transaction with their wallets for three months before the start of our project. By targeting this group, we hypothesise that high transaction fees (i.e. withdrawal fees) could be among the reasons for low account usage among these clients. Hence, to test this hypothesis, we expose a random sample of these clients to three different withdrawal subsidies. Each withdrawal subsidy involves the discounting of the current withdrawal fees of the service provider.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
1. Average number of cash-outs per month
2. Average number of cash-ins per month
3. Monthly average net Wallet balance
4. Average number of transfers per month

All the above stated outcomes will be collected from the administrative data of the partner financial institution. They will keep track of how the participants are using their accounts during the intervention and will share this information with us regularly.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
cash-out fees
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
In this experiment, we create exogenous variation in withdrawal fees to identify the effect of withdrawal subsidies on usage of mobile money services. To this effect, our experiment consists of three experimental arms; one control arm and 2 treatment arms. The three arms are one of three withdrawal fee discounts: 0%, 15%, and 30%. Selected Qodoo clients for the experiment are assigned to one of these three arms or withdrawal fee discounts. Therefore, the control group will consist of clients in the experimental sample that is randomly assigned to the 0% withdrawal discount. The two treatment arms, therefore, consist of participants in the experimental sample who are randomly assigned to either the 15% or 30% withdrawal discount treatment. For all treatments, the withdrawal fee discounts involve the discounting of the current cash-out schedule of the partner financial institution (Qodoo mobile money) by the withdrawal discount of the respective treatment, and is applicable to transaction amounts not more than 5,000.
Experimental Design Details
Randomization Method
Simple random assignment of selected participants into control and treatment arms. Randomization will be done using STATA.
Randomization Unit
In-active Clients of Qodoo Financial Services. That is Clients that have not used their wallets for three months before our Intervention.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
2625 inactive clients
Sample size: planned number of observations
2625 In-active clients
Sample size (or number of clusters) by treatment arms
Allocation of sample to 3 arms: 40% (1050 clients) to control and 60% (1575 clients) to treatment arm. Each treatment arm receives 1/2 of the 60% (about 788 clients).
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
The parameters used for the power analysis are calibrated based on net wallet balance and cash-ins of the target group, and sample size is determined after adjusting for 54% take-up rates; take-up rates in the literature ranges from 8.7% in Karlan & Zinman (2009) to about 54.7% in Kast et al. (2016). Thus, our assumption on take-up rates is on the upper bound of the range found in the literature. This is motivated by the fact that the intervention target existing clients, and there are strong incentives for participation. We also assume a MDE of 0.135 standard deviations on net monthly wallet balance and cash-ins; this is in line with the literature (such as Dupas et al.,2016; Karlan and Zinman, 2018) who find similar effect size for account balance in the case of commitment savings. Furthermore, we assume a 5% level of significance and 80% level of power.

Institutional Review Boards (IRBs)

IRB Name
Partnership for Economic Policy PIERI Ethics Committee
IRB Approval Date
IRB Approval Number


Post Trial Information

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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