“Why Do Defaults Affect Behavior: Experimental Evidence from Afghanistan,” with Joshua Blumenstock and Michael Callen, American Economic Review, 2018, 108(10): 2868-2901. [PDF] [Published Version]
We report on an experiment examining why default options impact behavior. By randomly assigning employees to different varieties of a salary-linked savings account, we find that default enrollment increases participation by 40 percentage points---an effect equivalent to providing a 50% matching incentive. We then use a series of experimental interventions to differentiate between explanations for the default effect, which we conclude is driven largely by present-biased preferences and the cognitive cost of thinking through different savings scenarios. Default assignment also changes employees' attitudes toward saving, and makes them more likely to actively decide to save after the study concludes.
“Relationships on the Rocks: Contract Evolution in a Market for Ice,” with Tristan Reed, American Economic Journal: Microeconomics, 2022, 14(1): 330-365. [PDF] [Published Version]
Firms use relational contracts to support repeated trade. Do these informal agreements evolve in response to market conditions? In a market for ice, firms reestablish relationships on new terms when a prior agreement breaks down. Using transaction data, we show that ice retailers prioritize deliveries to loyal buyers -- fishing firms -- when supply from the monopolistic manufacturer is scarce. After an upstream competition shock increases supply, repeated trade lapses, threatening retailers' positions. Incumbent retailers establish a new agreement expanding trade credit to loyal buyers, which impedes new retailer entry. Upstream competition also increases downstream firms' productivity and lowers consumer fish prices.
“Violence and Financial Decisions: Evidence from Mobile Money in Afghanistan,” with Joshua Blumenstock, Michael Callen and Robert Gonzalez, 2024, 106 (2): 352–369, Review of Economics & Statistics. [PDF] [Published Version]
We provide evidence that violence reduces the adoption and use of mobile money in three separate empirical settings in Afghanistan. First, we spatially merge nationwide administrative data on 96,000 violent events with the universe of mobile money transactions and find that users exposed to nearby violence reduce their mobile money account balances and conduct fewer transactions. Second, using high-frequency panel survey data from a field experiment, we find that subjects expecting violence are half as likely to respond to a randomized mobile money supply shock as those not expecting violence. Finally, analyzing financial survey data from nineteen of Afghanistan's 34 provinces, we find that individuals expecting violence hold more cash. Collectively, our evidence suggests that violence can impede the growth of formal financial systems.
“Mining Competition and Violent Conflict in Africa: Pitting Against Each Other,” with Juan Lozano, Anouk Rigterink and Jacob Shapiro, 2025, 87(1): 99-114, Journal of Politics. [PDF] [Published Version]
Existing explanations for the well-established relationship between mining and conflict predominantly interpret violence near mines as conflict over territory or government. We provide evidence that competition between artisanal and industrial miners is also an important source of natural resources-related conflict, drawing on qualitative case studies at mining sites in the Democratic Republic of Congo and Zimbabwe, and a large-N analysis. For the latter, we use machine learning to estimate the feasibility of artisanal mining across the continent of Africa based on geological conditions. The impact of price shocks on violent conflict is over three times larger in locations with industrial mining where artisanal mining is feasible than in places with industrial mining unsuitable for artisanal mining. Our estimates suggest that 31 to 55% of the observed mining-conflict relationship is due to violent industrial-artisanal miner competition. This implies new avenues for conflict-mitigation as the clean energy transition increases demand for minerals.
“Can Digital Aid Deliver During Humanitarian Crises?” with Michael Callen, Miguel Fajarado-Steinhauser and Michael Findley, Forthcoming, Management Science. [PDF] [Published Version]
Can digital payments help reduce extreme hunger? Humanitarian needs are at their highest since 1945, aid budgets are falling behind, and hunger is concentrating in fragile states where repression and aid diversion present major obstacles. In such contexts, partnering directly with governments is often neither feasible nor desirable, making private digital payment platforms a potentially useful means of delivering assistance. We experimentally evaluated digital payments to extremely poor, female-headed households in Afghanistan, as part of a partnership between community, nonprofit, and private organizations. The payments led to substantial improvements in food security and mental well-being. Despite beneficiaries' limited tech literacy, 99.75% used the payments, and stringent checks revealed no evidence of diversion. Before seeing our results, policymakers and experts are uncertain and skeptical about digital aid, consistent with the lack of prior evidence on digital payments for humanitarian response. Delivery costs are under 7 cents per dollar, which is 10 cents per dollar less than the World Food Programme's global figure for cash-based transfers. These savings can help reduce hunger without additional resources, demonstrating how hybrid partnerships utilizing digital payment platforms can help address grand challenges in difficult contexts.
“Insecurity and Firm Displacement: Evidence from Afghan Corporate Phone Records,” with Joshua Blumenstock, Sylvan Herskowitz, Ethan Kapstein, Thomas Scherer and Ott Toomet, Forthcoming, American Economic Journal: Economic Policy. [PDF] [Published Version]
We provide empirical evidence on how insecurity affects firm behavior by linking data on deadly terrorist attacks in Afghanistan to geolocated data on corporate mobile phone activity. We first develop an approach to estimate the geographic footprint of firms from employee locations. Using these measures, our main analysis finds that violent shocks reduce local firm presence by both increasing firm exit and decreasing entry. Firms react most to violence in their ‘headquarters’ district. We further find suggestive evidence of persistence, stronger impacts in more secure districts, and spillovers, whereby attacks in provincial capitals reduce firm presence in surrounding rural districts.
“Strengthening Fragile States: Evidence from Mobile Salary Payments in Afghanistan,” with Joshua Blumenstock, Michael Callen, Anastasiia Faikina and Stefano Fiorin. (R&R, Review of Economic Studies) [PDF]
We conduct a randomized evaluation of a flagship Afghan government initiative aimed at building state administrative capacity during a period when the state faced existential uncertainty. The program aimed to modernize employee tracking and salary payments in the Ministry of Education through biometric registration and digital payment systems. The reform reduced payment delays, decreased teacher turnover, modestly improved student learning outcomes, and expanded financial inclusion, though delays increased substantially during the first year. Employee enrollment was higher in districts where citizens had greater confidence in and consensus about the government’s prospects to defeat the Taliban. These findings indicate that building administrative capacity can improve state performance in fragile states, and suggest that the existential uncertainty inherent in state fragility hinders the development of such state capacity.