Case Study

Defaults and Donation


The poor in Kenya cannot afford health insurance, and so must pay for their medical expenses out of pocket. Unfortunately, the savings rate for health expenses is very low. This multiplies the impact of health-related emergencies, as people often do not have enough money to cover the cost of medical bills even when they have saved. Given that a nationally subsidized health insurance costs about $60 per year, there is an opportunity to create a peer-to-peer charitable giving platform to promote co-funding of health insurance for a Kenyan family. The Global Health and Development team is helping to optimize the design of such a platform.


As part of the design process, we tested the impact of preselected, or default, donation amounts on donation. We predicted that providing larger defaults would lead to higher donations, but fewer donors overall.

We tested a prototype of the Mbrella mobile site on Amazon Mechanical Turk. Participants could choose whether they wanted to be matched with a recipient based on their answers to three questions (the homophily condition), or at random (the random match condition).

Once on the donation page, participants saw one of three default amounts: $5, $30, or $55.

We measured frequency of donation, as well as the average donation amount in each condition.


We found that participants gave slightly more and more often after they had chosen to answer the homophily conditions compared to after they had chosen to be randomly matched. We also found that default had a significant effect on donation amount such that the $30 and $55 defaults led to higher donations compared to the $5 anchor. However, people donated more often when they saw a $30 default compared to when they saw a $55 default. Thus, our hypothesis was partially confirmed.

Additionally, we found that participants in the homophily condition chose to give more often than those in the random match condition, but only when they were given a $30 anchor.

Why it Matters

A moderate anchor generates the highest number of donations, and elicits donations comparable in size to larger anchors. Moderate anchors are also highly effective in eliciting donations from users who are willing to engage more with potential recipients.