NEW UPDATE: Completed trials may now upload and register supplementary documents (e.g. null results reports, populated pre-analysis plans, or post-trial results reports) in the Post Trial section under Reports, Papers, & Other Materials.
Voucher Experiment - Intervention to fight anemia and improve well-being in a very low income setting
Last registered on November 21, 2013


Trial Information
General Information
Voucher Experiment - Intervention to fight anemia and improve well-being in a very low income setting
Initial registration date
Not yet registered
Last updated
November 21, 2013 12:22 PM EST
Primary Investigator
CESS Nuffield - FLAME University
Other Primary Investigator(s)
PI Affiliation
PI Affiliation
Additional Trial Information
On going
Start date
End date
Secondary IDs
Iron deficiency anemia (IDA) has been linked to low productivity in adults, slowing of cognitive and physical growth among children and, in the elderly, increased risk of cognitive impairment and physical disability, as well as decreased muscle strength.

Distributing iron supplements appears to be an impractical policy in resource-poor settings where the public health systems do not have the capacity to maintain a large-scale distribution system. Iron supplementation of foods is therefore an attractive alternative: it requires no additional effort on the part of the consumer, and can be done relatively cheaply in centralized locations. While NIN's Iron (and Iodine) Fortified Salt (DFS) has been studied extensively by the National Institute of Nutrition (Hyderabad) and others for safety and efficacy in humans, willingness to pay for this new technology has not been established.

Stores in 200 villages have been stocked with DFS as a part of a larger experiment.

In this experiment, we distribute vouchers to 15 sample households in each of 150 randomly assigned villages (voucher is a flyer mentioning that Double Fortified Salt is available at a discounted price for limited time at stores in their village) in order to estimate the impact of information given directly to households on DFS take-up. The remaining 50 villages are assigned to the control condition.

External Link(s)
Registration Citation
Banerjee, Abhijit, Sharon Barnhardt and Esther Duflo. 2013. "Voucher Experiment - Intervention to fight anemia and improve well-being in a very low income setting." AEA RCT Registry. November 21. https://doi.org/10.1257/rct.109-1.0.
Sponsors & Partners

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

Request Information
Experimental Details
The voucher is a small flyer that advertises the availability of Tata Salt Plus (iron and iodine fortified) at a special price for an unspecified limited time at stores in the village. This allows us to identify the impact of information about product existence given in the household on purchases.

In the treatment villages, the voucher is delivered to the household. In control villages, no one receives a voucher. The salt is available for purchase in both control and treatment villages.
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
DFS purchase
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
The 200 villages where we work are part of a larger experiment in which we have randomly assigned 200 villages where we make DFS available for purchase and 200 villages where we do not introduce DFS. This voucher trial takes place in the 200 villages where salt is being sold.

We are already conducting other trials in these villages, which means we further stratify the sample of 200 villages by their experimental groups before randomly assigning 75% in each strata to the voucher condition and 25% to the control condition.

The experimental groups that make up the strata are created as follows (and are registered separately in this registry):
1. What is the impact of free DFS on health? In randomly assigned villages, a randomly assigned subset of households are being given free salt. In control villages no households are given free DFS. [2 groups]
2. What is the impact of providing entertaining information about DFS on sales? In randomly assigned villages, a short and entertaining film about DFS is shown publicly. In the remaining control villages no short film is shown. [2 groups]
3. Can sales be increased by incentivizing individual retail outlets to increase sales? This experiment divides villages into 3 groups after excluding villages without more than 1 private store: all private stores in the village get a temporary discount on DFS, 1 private store gets the temporary discount, and (the control) no stores get a temporary discount. [4 groups including those excluded from randomization]

Thus, in all there are 16 strata. In each strata the villages are randomly assigned as mentioned above (in 75% of the villages 15 study households are given vouchers, in the control 25% of villages 15 study households are not given vouchers).
Experimental Design Details
Randomization Method
Done in office by a computer
Randomization Unit
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
3000 households across 200 villages
Sample size: planned number of observations
3000 households
Sample size (or number of clusters) by treatment arms
50 villages control
150 villages vouchers (flyers)
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
IRB Approval Date
IRB Approval Number
Post Trial Information
Study Withdrawal
Is the intervention completed?
Is data collection complete?
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports, Papers & Other Materials
Relevant Paper(s)