Using data from a field experiment in Kenya, we document that providing individuals with simple informal savings technologies can substantially increase investment in preventative health and reduce vulnerability to health shocks. Simply providing a safe place to keep money was sufficient to increase health savings by 66 percent. Adding an earmarking feature was only helpful when funds were put toward emergencies, or for individuals that are frequently taxed by friends and relatives. Group-based savings and credit schemes had very large effects.

Coping with Political Instability: Micro Evidence from Kenya's 2007 Election Crisis by Pascaline Dupas and Jonathan Robinson. Published in volume 100, issue 2, pages 120-24 of American Economic Review, May 2010

Abstract We test whether the provision of multiple labeled savings accounts affects savings and downstream outcomes in an experiment with 761 microentrepreneurs in urban Malawi. Treatment respondents received one or multiple savings accounts, in the form of lockboxes or mobile money. We find that while providing additional boxes increased savings by 40%, technical issues marred the efficacy of a second mobile money account. Data from novel high-frequency surveys suggest that both types of accounts had impacts on downstream outcomes, including farming decisions and credit extended to customers. We do not detect differential downstream effects by the number or modality of accounts.

We model farmers as facing small fixed costs of purchasing fertilizer and assume some are stochastically present biased and not fully sophisticated about this bias. Such farmers may procrastinate, postponing fertilizer purchases until later periods, when they may be too impatient to purchase fertilizer. Consistent with the model, many farmers in Western Kenya fail to take advantage of apparently profitable fertilizer investments, but they do invest in response to small, time-limited discounts on the cost of acquiring fertilizer (free delivery) just after harvest. Calibration suggests that this policy can yield higher welfare than either laissez-faire policies or heavy subsidies. (JEL Q13, Q12, Q16, Q18)

How High Are Rates of Return to Fertilizer? Evidence from Field Experiments in Kenya by Esther Duflo, Michael Kremer and Jonathan Robinson. Published in volume 98, issue 2, pages 482-88 of American Economic Review, May 2008

Abstract We collect data on prices, travel costs, and farmer decisions to quantify market access for chemical fertilizer and its impact on agricultural productivity in 1,180 villages in Northern Tanzania. Villages at the bottom of the travel cost-adjusted input price distribution face 40%–55% less favorable prices than those at the top. A standard deviation increase in village-level remoteness is associated with 20%–25% lower input adoption. A spatial model of input adoption conservatively estimates that total trade costs are 4 times pecuniary travel costs. Counterfactuals suggest that halving travel costs would more than double adoption and reduce the adoption-remoteness gradient by 63%.