Learning About a Warming World: Attention and Adaptation in Agriculture
Global warming threatens the livelihoods of 600 million low-income agricultural workers. I study how farmers learn about the environment and the consequences for climate change adaptation. Rice farmers in Bangladesh must form beliefs about local soil salinity, a climate danger exacerbated by rising sea levels that can be mitigated by planting salinity-tolerant seeds. Comparing beliefs about salt levels to agronomic readings, I find that on average farmers hold correct environmental perceptions, but this masks substantial errors across individuals. To explain this pattern, I build a belief formation model with a fundamental identification problem: farmers must learn about many environmental threats from relatively few signals. As a result, farmers endogenously process ambiguous data in support of their priors, e.g., someone worried about high salinity will interpret low yield as a sign of too much salt. Climate change amplifies this process by systematically altering the environmental risks farmers consider most threatening. I test and confirm the model's predictions using a pair of natural experiments that capture two changes emblematic of global warming: salient shocks that capture attention (e.g., tidal flooding) and subtle shifts that go unnoticed (e.g., groundwater contamination through rising sea-levels). Despite equal effects on true salt levels, I find asymmetric impacts on beliefs as subtle groundwater intrusion causes no change in perceptions while saltwater floods spur significant overestimation. Analyses of rainfall and flooding perceptions exhibit similar patterns to those of soil salinity. In large-scale field experiments, I document major economic consequences of environmental beliefs: correcting misperceptions significantly alters farmers' demand for salinity-tolerant seeds with substantial impacts on profits. I use this experimental variation to estimate and validate a structural model of seed choice that allows me to simulate counterfactual policies and underscores the influence of environmental beliefs.
| PDF | Survey Instruments
Baseline (English) | Baseline (Bangla) | Endline (English) | Endline (Bangla)
| World Bank Blog
[Online Interactive Guide: How to Measure Floods from Space]
Floods threaten the livelihood of a quarter of the world's population, most of whom live in poor countries. How do floods impact economic development, and how do households adapt? To answer these questions, I first combine methods from geophysics and machine learning in the analysis of satellite data to detect inundation at a granular geographic level anywhere every day for the past two decades. Using this approach in Bangladesh, I find that floods cause a persistent decline in economic activity and force structural change by pushing employment out of agriculture, spurring migration, and shifting children into school. Places with recent exposure to floods experience less harm after subsequent inundation. Using a simple model of experience-driven adaptation, I derive empirical tests for two mechanisms underpinning this pattern and find evidence for both. In a survey of rural farmers, I first show that past flood exposure increases the perceived marginal benefit of adaptation investment by raising households' beliefs about future disaster risk and damages. I next find that the marginal cost of coping with floods via temporary urban migration declines in inundation experience. Consistent with this "learning-by-doing" channel, reduced mobility frictions identified from quasi-random variation in Colonial-era transportation networks mediate the differential treatment effects of past flood exposure. Together, my results indicate that endogenous adaptation will significantly reduce the damage from future flooding.
What Jobs Come to Mind? Stereotypes About Fields of Study
(with John J. Conlon)
Using both large-scale nationally representative data and surveys administered among undergraduates at the Ohio State University, we document that US freshmen hold systematic misperceptions about the relationship between college majors and occupations. Students stereotype fields of study, greatly exaggerating the likelihood that majors lead to their distinctive jobs (e.g., counselor for psychology, journalist for journalism). In a field experiment, we find that reducing stereotyping has significant effects on students' intentions about what to study as well as the classes and majors they actually choose. Finally, we present a model of belief formation in which stereotyping arises as a product of associative recall. The model makes additional predictions—which new survey evidence broadly confirms—both about average beliefs and how heterogeneity in beliefs should systematically depend on the careers and majors of people students know personally.
| PDF | Coverage
Econimate Video Summary
A Rosetta Stone for Human Capital
(with Justin Sandefur)
International comparisons of human capital figure prominently in economists' explanations of poverty, economic growth, and trade patterns. But how can we accurately measure the global distribution of skills when countries do not take the same tests? We develop a new methodology to non-parametrically link scores from distinct populations. By administering an exam combining items from different assessments to 2,300 primary students in India, we estimate conversion functions among four of the world's largest standardized tests spanning 80 countries. Armed with this learning "Rosetta Stone", we revisit various well-known results, showing, inter alia, that learning differences between most- and least-developed countries are larger than existing estimates suggest. Applying our translations to microdata, we match pupils' socio-economic status to moments of the global income distribution and document several novel facts: (i) students with the same household income score significantly higher if they live in richer countries; (ii) the income-test score gradient is steeper in countries with greater income inequality; (iii) girls read better than boys at all incomes but only outperform them in mathematics at the lowest deciles of the global income distribution; and (iv) the test-score gap between public and private schools increases with inequality, partially due to a rise in socio-economic sorting across school types.
| PDF | Coverage
Risk Sharing and Adaptation to Environmental Threats
Risk sharing among neighbors provides an important way to smooth consumption in developing countries. I study how the spatial covariance typical of environmental threats shapes risk sharing in a dynamic limited commitment model. Households allocate economic activity between local and distant production and choose whether to engage in informal village risk sharing. The degree of local insurance depends on the relative riskiness of production outside the village. Higher spatial concentration of shocks can increase reliance on neighbors when households' outside option carries sufficient risk. In a survey of Bangladeshi farmers, I find that households facing higher shock covariances send more family members to cities where they find employment and participate more in informal insurance networks within their village.
Marriage Markets and the Gender Pay Gap
Women with higher-paid husbands work less and earn less when they are employed. I build a multi-period model of the marriage market and subsequent spousal labor supply decisions to illustrate two potential channels underlying this fact: selection in the spousal match and treatment from partner type. Exploiting the sharp changes in the gender composition of college campuses in the U.S. around World War II, I isolate the treatment effect of the market for potential husbands. Women facing a dating pool with more college-educated men work and earn significantly less during the next 30 years. Those who do enter the labor force ultimately work fewer hours and choose more flexible, lower paying occupations and industries.
Women's Urban Mobility Barriers: Evidence from Delhi's Free Public Transport Policy
(with Girija Borker and Gabriel Kreindler)
Women's mobility is severely restricted in many cities in developing countries. We study these constraints in the setting of a unique policy in Delhi, India that made public buses free for women citywide and added bus marshals on all buses. Using detailed panel survey data for a sample of women with low socio-economic status, we cannot detect an effect of the policy on mobility, despite a large citywide increase in female bus ridership and high policy awareness. In a randomized experiment before the citywide policy, we delivered a free one-month bus pass to women in the same sample. We find large effects on overall mobility that persist after the citywide policy is enacted and the bus pass becomes obsolete. These results are consistent with large individual-level frictions in mobility behavior that can be relaxed by a personalized intervention.
Texts Don't Nudge: An Adaptive Trial to Prevent the Spread of COVID-19 in India
(with Girija Bahety, Sebastian Bauhoff, and James Potter)
Journal of Development Economics (2021)
We conduct an adaptive randomized controlled trial to evaluate the impact of a SMS-based information campaign on the adoption of social distancing and handwashing in rural Bihar, India, six months into the COVID-19 pandemic. We test 10 arms that vary in delivery timing and message framing, changing content to highlight gains or losses for either one's own family or community. We identify the optimal treatment separately for each targeted behavior by adaptively allocating shares across arms over 10 experimental rounds using exploration sampling. Based on phone surveys with nearly 4,000 households and using several elicitation methods, we do not find evidence of impact on knowledge or adoption of preventive health behavior, and our confidence intervals cannot rule out positive effects as large as 5.5 percentage points, or 16%. Our results suggest that SMS-based information campaigns may have limited efficacy after the initial phase of a pandemic.
| PDF | Replication Materials
The New Era of Unconditional Convergence
(with Arvind Subramanian and Justin Sandefur)
Journal of Development Economics (2021)
The central fact that has motivated the empirics of economic growth—namely unconditional divergence—is no longer true and has not been so for decades. Across a range of data sources, poorer countries have in fact been catching up with richer ones, albeit slowly, since the mid-1990s. This new era of convergence does not stem primarily from growth moderation in the rich world but rather from accelerating growth in the developing world, which has simultaneously become remarkably less volatile and more persistent. Debates about a "middle-income trap" also appear anachronistic: middle-income countries have exhibited higher growth rates than all others since the mid-1980s.
| PDF | Replication Materials
Replication Data and Code | Figures from the Paper
Bloomberg (Noah Smith) | The Economist | The New York Times (Paul Krugman)
Syllabus for my class on the economics of gender inequality
Bangladesh Data Resources
Bangladesh Labor Force Survey 2016-17
Roshni Islam translated the 2016-17 questionnaire to English. The underlying data can be acquired by contacting the Bangladesh Bureau of Statistics. For more details, visit this link.