small incentives – BIG IMPACT

The case of child immunisation

(c) J. F.

One of the cheapest and most effective ways to save a child’s life is through vaccination. Yet, every year at least 25 million children in the world don’t get fully immunised and an estimated 2 to 3 million people die from a disease that could have been prevented with a vaccine (J-PAL).

Why is this?

In many developing countries, there is only few or no health care provision and reliable vaccine supplies are scarce.

But, part of the problem too is that people are not well informed. Myths and misconceptions about immunisation and suspicion about public health services are ubiquitous and not confined to ‘the poors’. Just consider the rise of vaccine-sceptics and vaccine-opponents (who regularly voice themselves on media) and the recent surge of measles in Europe.

Yet, even where technology and infrastructure are in place (e.g. in India, where immunisation is offered for free in public health facilities), immunisation rates remain low. In psychology, this is called ‘a last mile problem’: the final hitch that prevents people from turning their intentions and plans into action

The opportunity cost of immunisation

The tribal villages of Udaipur district in Rajasthan, India, represent an extreme case of ‘last mile problem’: there, only 2% of children aged 1 to 2 are fully immunised. Health facilities serving these rural areas are often located kilometers away from where people live. For mothers, getting each of their infants immunised, means shouldering a long walk to a sub-center – 5 times back and forth (basic immunisation = 5 visits). But even when they eventually get there, the odds that the health facility will  be closed (because nurses are absent for no apparent reason) are high.

So, in essence, logistical hurdles and unreliability of health services are the main reasons why families don’t get their children immunised.

Make it easy  & give people a reason to act

A team of researchers around Esther Duflo and Abhijit Banerjee decided to tackle this issue by conducting a randomised controlled trial in 134 villages in Udaipur with almost 2,000 children. Although randomised controlled trials (RCTs) are state of the art in medical research, they have been given little or no attention in social policy.

white box: what is a randomised controlled trial? 

A standard medical experiment looks like this: People are allocated at random (by chance) to one of two groups: either the treatment group or the control group (which serves as standard of comparison). Those in the first group get a medical treatment, while those in the second group receive a placebo or no treatment at all. The aim is to observe whether a treatment has an effect. And if so, which effect. 

Now, in the case of villages in Udaipur, the researchers trialled 2 interventions:

Intervention A : Make it easy for people to get immunised by organising monthly immunisation camps (treatment group 1)

Intervention B : Make it easy and give people a reason to act now by installing monthly immunisation camps and by offering families 1 kg of lentils per immunisation (treatment group 2). 1 kg of lentils is worth about 40 rupees (less than 1$), which is equivalent to three quarters of a daily wage.  


Status quo :  leave everything as it was (control group)

What were the results of this experiment? 

Organising monthly immunisation camps (intervention A) raised the rate of child immunisation by 11 percentage points relative to the control group.

However, even more compelling: setting up immunisation camps and offering lentils to families (intervention B) multiplied immunisation coverage by more than 6 times and secured immunisation for 38% of children.

It may surprise you that intervention B also turned out to be the most cost-effective option. When a monthly camp is installed, immunisation costs 50 $ per child. It only costs 27 $ when lentils are added as incentive. This is because, in any case, a nurse has to be paid. But, the more children come to a camp, the less the cost of a nurse per child because of scale economies. 

Lessons to be learned 

Small incentives can have a BIG impact

Money (or financial aid) is only part of the solution

Put yourself in the shoes of the people concerned

Take the guesswork out of policy making: instead, trial to know what works, what doesn’t and why?

Base yourself on evidence rather than on ideology and arbitrariness

⇨ We may not be able to answer the big questions: how to fight poverty on a global scale or how to ensure economic and social development? But, we can provide answers to the smaller questions that make up the bigger question: how to improve child immunisation? how to get children into education?…

Esther Duflo, Abhijit Banerjee and Michael Kremer were this year’s laureates of the Nobel prize in economics for “their experimental approach to alleviating global poverty”.

On a personal note: Esther Duflo has also been an inspirational figure for my own academic path. In 2012, I incidentally watched a documentary on development aid. In it, Duflo explained how experimentation could inform social policy. The ‘lentils-experiment’ left a lasting impression on me and made me want to pursue studies in behavioural science


  Written and published November 2019

by Jessica 


References I used in this article:

Banerjee, A., Deaton A., and Duflo E. (2004). Health Care Delivery in Rural Rajasthan. Economic and Political Weekly: 944-99.

Banerjee, A., Duflo E., Glennerster R., and Kothari D. (2010). Improving Immunisation Coverage in Rural India: Clustered Randomised Controlled Evaluation of Immunisation Campaigns with and without Incentives. BMJ 340-222.

J-PAL (Abdul Latif Jameel Poverty Action Lab)

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