research

journal articles

1. Filling a niche? The maize productivity impacts of adaptive breeding by a local seed company in Kenya

   Samuel S. Bird, Michael R. Carter, Travis J. Lybbert, Mary Mathenge, Timothy Njagi, and Emilia Tjernström

   Journal of Development Economics, 2022

   abstract link

   This paper studies whether the absence of locally adapted seed varieties constrains the productivity and incomes of farm households residing in small, agro-ecological niches. We empirically examine the disruption of the maize seed market in Western Kenya that took place when public sector foundation breeding and social impact investment capital came together and allowed a local seed company to expand and target a niche area with adaptively-bred maize varieties. The three-year randomized controlled trial reveals that these seed varieties increased farmer yields and revenues, both for better-resourced farmers (who used non-adapted hybrids and fertilizer prior to the intervention) as well as less well-resourced farmers (who did not). This theoretical and empirical evidence suggests news ways for thinking about seed systems in areas typified by high levels of agro-ecological heterogeneity.

2. Learning by (Virtually) Doing: Experimentation and Belief Updating in Smallholder Agriculture

   Emilia Tjernström, Travis J. Lybbert, Rachel Frattarola Hernández, and Juan Sebastian Correa

   Journal of Economic Behavior & Organization, 2021

   abstract link

   In much of sub-Saharan Africa, soil quality heterogeneity hampers farmer learning about the returns to different inputs. This may help explain why relatively few farmers in the region use improved inputs. We study how Kenyan farmers respond to an interactive app that enables them to discover the returns to different inputs on a virtual farm that is calibrated to resemble their own. Farmers update both their beliefs and their behaviors after engaging with the virtual learning app. We measure beliefs by eliciting probability distributions and use an incentive-compatible experiment to measure behavior change. The experiment gave participants an input budget that they could allocate across farm inputs. After playing several virtual seasons on the app, they could update these allocations. Farmers revise their input allocations along several dimensions after the virtual learning experience. To support our interpretation that these adjustments stem from real learning, we show that farmers with the highest predicted returns to lime—an unfamiliar input in this region—increase their lime orders more than others. Our results suggest that engagement with a personalized virtual platform can induce real learning and enhance farmers’ beliefs and technology choices.

3. Heterogeneous Impact Dynamics of a Rural Business Development Program in Nicaragua

   Michael R. Carter, Emilia Tjernström, and Patricia Toledo

   Journal of Development Economics, 2019

   abstract link

   We study the impacts of a rural development program designed to boost the income of the small-farm sector in Nicaragua. Exploiting the random assignment of treatment, we find statistically and economically significant impacts on gross farm income and investment in productive farm capital. Using continuous treatment estimation techniques, we examine the evolution of program impacts over time and find that the estimated income increase persists and that the impacts on productive capital stock continue to rise even after the program concluded. Additionally, panel quantile methods reveal striking heterogeneity of program impacts on both income and investment. We show that this heterogeneity is not random and that there appear to exist low-performing household types who benefit little from the program, whereas high-performing (upper quantile) households benefit more substantially. Analysis using generalized random forests, a machine learning algorithm, points toward greater program impacts for households who were disadvantaged at baseline. Even after controlling for this source of heterogeneity, we find large and persistent differences in how much different types of households benefited from the program. While the benefit-cost ratio of the program is on average positive, the impact heterogeneity suggests that business development programs aiming to engage farm households as agricultural entrepreneurs have limitations as instruments to eliminate rural poverty.

4. Money Matters: The Role of Yields and Profits in Agricultural Technology Adoption

   Jeffrey D. Michler, Emilia Tjernström, Simone Verkaart, and Kai Mausch

   American Journal of Agricultural Economics, 2019

   abstract link

   Despite the growing attention to technology adoption in the economics literature, knowledge gaps remain regarding why some valuable technologies are rapidly adopted, while others are not. This paper contributes to our understanding of agricultural technology adoption by showing that a focus on yield gains may, in some contexts, be misguided. We study a technology in Ethiopia that has no impact on yields, but that has nonetheless been widely adopted. Using three waves of panel data, we estimate a correlated random coefficient model and calculate the returns to improved chickpea in terms of yields, costs, and profits. We find that farmers’ comparative advantage does not play a significant role in their adoption decisions and hypothesize that this is due to the overall high economic returns to adoption, despite the limited yield impacts of the technology. Our results suggest economic measures of returns may be more relevant than increases in yields in explaining technology adoption decisions.

5. Fitting and Interpreting Correlated Random Coefficient (CRC) Models Using Stata

   Oscar Barriga Cabanillas, Jeffrey D. Michler, Aleksandr Michuda, and Emilia Tjernström

   Stata Journal, 2018

   abstract link PDF

   In this article, we introduce the community-contributed command randcoef, which fits the correlated random-effects and correlated random-coefficient models discussed in Suri (2011, Econometrica 79: 159-209). While this approach has been around for a decade, its use has been limited by the computationally intensive nature of the estimation procedure that relies on the optimal minimum distance estimator. randcoef can accommodate up to five rounds of panel data and offers several options, including alternative weight matrices for estimation and inclusion of additional endogenous regressors. We also present postestimation analysis using sample data to facilitate understanding and interpretation of results

6. Natural Disasters, Social Protection, and Risk Perceptions

   Philip Brown, Adam J. Daigneault, Emilia Tjernström, and Wenbo Zou

   World Development, 2018

   abstract link

   Natural disasters give rise to loss and damage and may affect subjective expectations about the prevalence and severity of future disasters. These expectations might then in turn shape individuals’ investment behaviors, potentially affecting their incomes in subsequent years. As part of an emerging literature on endogenous preferences, economists have begun studying the consequences that exposure to natural disasters have on risk attitudes, perceptions, and behavior. We add to this field by studying the impact of being struck by the December 2012 Cyclone Evan on Fijian households’ risk attitudes and subjective expectations about the likelihood and severity of natural disasters over the next 20 years. The randomness of the cyclone’s path allows us to estimate the causal effects of exposure on both risk attitudes and risk perceptions. Our results show that being struck by an extreme event substantially changes individuals’ risk perceptions as well as their beliefs about the frequency and magnitude of future shocks. However, we find sharply distinct results for the two ethnicities in our sample, indigenous Fijians and Indo-Fijians; the impact of the natural disaster aligns with previous results in the literature on risk attitudes and risk perceptions for Indo-Fijians, whereas they have little to no impact on those same measures for indigenous Fijians.

7. Identifying the Impact Dynamics of a Small Farmer Development Scheme in Nicaragua

   Emilia Tjernström, Michael R. Carter, and Patricia Toledo

   American Journal of Agricultural Economics, Papers and Proceedings, 2013

   link

8. Do Differences in Attitudes Explain Differences in National Climate Change Policies?

   Emilia Tjernström, and Thomas H. Tietenberg

   Ecological Economics, 2008

9. Rational Foolishness Would Destroy a Public Service Broadcasting System

   Sune Tjernström, and Emilia Tjernström

   Journal of Media Economics, 2008

working papers

1. Comment on Suri (2011) "Selection and Comparative Advantage in Technology Adoption"

   Emilia Tjernström, Dalia Ghanem, Oscar Barriga Cabanillas, Travis Lybbert, Aleksandr Michuda, and Jeffrey Michler

   2024

   Revision invited at Econometrica

   abstract PDF

   This paper illustrates and addresses weak identification concerns in the correlated random coefficient (CRC) model that Suri (2011) uses to study agricultural technology adoption. Using the publicly available version of the dataset used in Suri (2011), which we clean following the author’s instructions, we are unable to replicate the paper’s main CRC model results. To understand why, we recast the CRC model as a more general random-coefficient model in which the returns to hybrid adoption are restricted to be linear in comparative advantage. This reveals that the key structural parameter in the CRC model (φ) is prone to a weak identification problem. We then propose a procedure to conduct weak-identification robust inference on φusing test inversion. Only with this robust procedure accounting for weak identification are we able to replicate the original Suri (2011) results.

2. 

   Relaxing Multiple Agricultural Productivity Constraints at Scale

   Joshua W. Deutschmann, Maya Duru, Kim Siegal, and Emilia Tjernström

   2024

   Revision invited at Journal of Development Economics

   abstract pre-reg PDF

   No single constraint can explain the stagnant agricultural productivity growth in sub-Saharan Africa. Most interventions that relax individual barriers to productivity have delivered disappointing results. We evaluate an at-scale program that targets several productivity constraints with a bundled intervention, using a randomized controlled trial in western Kenya. Program participation increases maize yields by 26%, total maize output by 24%, and profits by 17%. While we cannot directly test whether the program’s success is due to its bundled nature, we find patterns in the data that are consistent with this hypothesis.

3. Selection and Heterogeneity in the Returns to Migration

   Eduardo Cenci, Marieke Kleemans, and Emilia Tjernström

   2024

4. Media and Motivation: the Effect of Performance Pay on Writers and Content

   Ivan Balbuzanov, Jared Gars, and Emilia Tjernström

   2024

5. Air Pollution and Mental Well-being: Evidence from Australia

   Valentina Duque, Zachary Duretto, Josh Merfeld, and Emilia Tjernström

   2024

6. Learning from Others in Heterogeneous Environments

   Emilia Tjernström

   2019

   Previous version circulated under "Signals, Similarity, and Seeds: Social Learning in the Presence of Imperfect Information and Heterogeneity"

policy briefs

1. Diverse Soils and Inputs Challenge Recommendations to Maize Farmers in Kenya

   Emilia Tjernström, Michael Carter, and Travis J. Lybbert

   2017

   link

2. Local Seed Company Fills a Niche to Increase Maize Productivity in Kenya

   Michael Carter, Mary K. Mathenge, Sam Bird, Travis J. Lybbert, Timothy Njagi, and Emilia Tjernström

   2017

   link
3. Spurring Technological Innovation and Poverty Reduction? Evaluating the Impact of a New Seed Market Actor in Kenya

   Michael R. Carter, Travis J. Lybbert, Mary K. Mathenge, and Emilia Tjernström

   2014

   link

4. Investing in Small-Farm Productivity: The Nicaragua MCC Compact

   Michael R. Carter, Emilia Tjernström, and Patricia Toledo

   2012

other writing

1. Agricultural Technology in Africa

   Tavneet Suri, Chris Udry, Jenny C Aker, Chris B. Barrett, Lauren Falcao Bergquist, Michael R. Carter, Lorenzo Casaburi, Robert Darko Osei, Doug Gollin, Vivian Hoffmann, Thomas Jayne, Naureen Karachiwalla, Haroun Kazianga, Jeremy Magruder, Hope Michelson, Meredith Startz, and Emilia Tjernström

   2024

   abstract link

   We discuss recent trends in agricultural productivity in Africa and highlight how technological progress in agriculture has stagnated on the continent. We briefly review the literature that tries to explain this stagnation through the lens of particular constraints to technology adoption. Ultimately, none of these constraints alone can explain these trends. New research highlights pervasive heterogeneity in the gross and net returns to agricultural technologies across Africa. We argue that this heterogeneity makes the adoption process more challenging, limits the scope of many innovations, and contributes to the stagnation in technology use. We conclude with directions for policy and what we feel are still important, unanswered research questions.

2. Price Premiums for Organic Strawberries

   Christine Carroll, Diane Charlton, and Emilia Tjernström

   2012

3. Kunnigt och (o)kontroversiellt om råvarumarknaden (Book review of “Handbook of Primary Commodities in the Global Economy” by Marian Radetzki)

   Emilia Tjernström

   2009