Tzachi Raz
@raztzachi.bsky.social
Assistant professor at HebrewU econ and PPE | PhD Harvard Econ | Economic History, Political Economy, Cultural Economics
https://www.tzachiraz.com/
https://www.tzachiraz.com/
Link to the paper: www.journals.uchicago.edu/doi/abs/10.1...
Soil Heterogeneity, Social Learning, and the Formation of Close-knit Communities | Journal of Political Economy: Vol 0, No ja
www.journals.uchicago.edu
March 4, 2025 at 11:03 AM
Link to the paper: www.journals.uchicago.edu/doi/abs/10.1...
The main takeaway is that environment conducive to beneficial social learning promotes the creation of interdependent social networks, shaping cultural and psychological traits within a short period
March 4, 2025 at 11:03 AM
The main takeaway is that environment conducive to beneficial social learning promotes the creation of interdependent social networks, shaping cultural and psychological traits within a short period
Finally, I examine the role of multiple confounding factors, competing mechanisms, and mediators, and provided suggestive evidence they did not play an important role. I also find that modernization is a potential mediator, but it can at most partially account for the impact
March 4, 2025 at 11:03 AM
Finally, I examine the role of multiple confounding factors, competing mechanisms, and mediators, and provided suggestive evidence they did not play an important role. I also find that modernization is a potential mediator, but it can at most partially account for the impact
Next, I explore selective out-migration. I document that local soil heterogeneity prompted farmers who who depended on social networks to migrate elsewhere. This finding is consistent with the DID results
March 4, 2025 at 11:03 AM
Next, I explore selective out-migration. I document that local soil heterogeneity prompted farmers who who depended on social networks to migrate elsewhere. This finding is consistent with the DID results
(3) the adverse impact of soil heterogeneity was concentrated in locations where the learning potential was high . In other words, if there was little to learn to begin with, not being able to learn from neighbors did not matter
March 4, 2025 at 11:03 AM
(3) the adverse impact of soil heterogeneity was concentrated in locations where the learning potential was high . In other words, if there was little to learn to begin with, not being able to learn from neighbors did not matter
(2) the adverse impact of soil heterogeneity on farmers’ learning is robust to controlling for the learning potential
March 4, 2025 at 11:03 AM
(2) the adverse impact of soil heterogeneity on farmers’ learning is robust to controlling for the learning potential
For both outcome I find that soil heterogeneity slowed farmers' learning and adaptation. Using GAEZ-FAO data I construct measures of the learning potential for the 2 outcomes, and show that (1) it positively affects learning,
March 4, 2025 at 11:03 AM
For both outcome I find that soil heterogeneity slowed farmers' learning and adaptation. Using GAEZ-FAO data I construct measures of the learning potential for the 2 outcomes, and show that (1) it positively affects learning,
Second, I provide implicit evidence by studying production outcomes, focusing on a historical context in which American farmers learned and adjusted their practices—the adaptation of wheat cultivation to marginal environments
March 4, 2025 at 11:03 AM
Second, I provide implicit evidence by studying production outcomes, focusing on a historical context in which American farmers learned and adjusted their practices—the adaptation of wheat cultivation to marginal environments
Exploring channels, I first document the negative impact of soil heterogeneity on farmers’ agricultural learning and adaptation. First, I use an explicit indicator of learning—the rate of fertilizer adoption in farms
March 4, 2025 at 11:03 AM
Exploring channels, I first document the negative impact of soil heterogeneity on farmers’ agricultural learning and adaptation. First, I use an explicit indicator of learning—the rate of fertilizer adoption in farms
I also explore the long-run impact on children’s communal attachment, and find that a child of a migrant to a soil-heterogeneous county was less likely to reside in it as an adult and less likely to marry a wife born in the destination state
March 4, 2025 at 11:03 AM
I also explore the long-run impact on children’s communal attachment, and find that a child of a migrant to a soil-heterogeneous county was less likely to reside in it as an adult and less likely to marry a wife born in the destination state
In line with the social learning hypothesis, the impact is immediate and concentrated in the first few years after the farmers arrived at a new location, when learning was crucial and new social ties were likely being formed
March 4, 2025 at 11:03 AM
In line with the social learning hypothesis, the impact is immediate and concentrated in the first few years after the farmers arrived at a new location, when learning was crucial and new social ties were likely being formed
The effect is concentrated on farmers with a prior communal disposition, which I interpret as indicating a pre-existing tendency to rely on social networks, leading to an "environmental mismatch" and high evolutionary pressure to adapt
March 4, 2025 at 11:03 AM
The effect is concentrated on farmers with a prior communal disposition, which I interpret as indicating a pre-existing tendency to rely on social networks, leading to an "environmental mismatch" and high evolutionary pressure to adapt
Using DID, I explore the short-run impact on in-group identity and document a decrease in communal identification among farmers who migrated to soil-heterogeneous counties compared to those who migrated to soil-homogeneous counties, with no impact on non-farmers
March 4, 2025 at 11:03 AM
Using DID, I explore the short-run impact on in-group identity and document a decrease in communal identification among farmers who migrated to soil-heterogeneous counties compared to those who migrated to soil-homogeneous counties, with no impact on non-farmers
I then proceed to present causal evidence on the formation of this association. I focus on 19th-century domestic migrants to explore selection and treatment effects. There's no evidence for selective in-migration based on prior farming experience or prior levels of communalism
March 4, 2025 at 11:03 AM
I then proceed to present causal evidence on the formation of this association. I focus on 19th-century domestic migrants to explore selection and treatment effects. There's no evidence for selective in-migration based on prior farming experience or prior levels of communalism
The impact has weakened over time but remains evident today
March 4, 2025 at 11:03 AM
The impact has weakened over time but remains evident today
First, I document a robust negative historical relationship between soil heterogeneity and close-knit communities with a county-level analysis and show that it is unlikely to be driven by selection on unobservables
March 4, 2025 at 11:03 AM
First, I document a robust negative historical relationship between soil heterogeneity and close-knit communities with a county-level analysis and show that it is unlikely to be driven by selection on unobservables
In the appendix, I also use three indicators focusing on kinship tightness. A separate 🧵 on all the historical indicators, along with data links is now forthcoming on Bluesky 😀
March 4, 2025 at 11:03 AM
In the appendix, I also use three indicators focusing on kinship tightness. A separate 🧵 on all the historical indicators, along with data links is now forthcoming on Bluesky 😀
the Intra-Community Marriage (ICM), capturing in-group bias, the Tight Norms Index (TNI), measuring the tightness of familial norms, and the Religious Homogeneity Index (RHI), capturing the tightness of religious identities and practices
March 4, 2025 at 11:03 AM
the Intra-Community Marriage (ICM), capturing in-group bias, the Tight Norms Index (TNI), measuring the tightness of familial norms, and the Religious Homogeneity Index (RHI), capturing the tightness of religious identities and practices
I also develop novel outcome variables measuring different cultural and psychological aspects of historically close-knit communities using census data: the Local Name Index (LNI), focusing on in-group identity and measured using children’s first names
March 4, 2025 at 11:03 AM
I also develop novel outcome variables measuring different cultural and psychological aspects of historically close-knit communities using census data: the Local Name Index (LNI), focusing on in-group identity and measured using children’s first names
I use detailed and highly-granular geo-referenced soil data to construct a county-level Soil Heterogeneity Index (SHI), capturing the average dissimilarity of soil across neighboring locations in the county
March 4, 2025 at 11:03 AM
I use detailed and highly-granular geo-referenced soil data to construct a county-level Soil Heterogeneity Index (SHI), capturing the average dissimilarity of soil across neighboring locations in the county
I provide the first empirical evidence supporting Shannon's (1945) Social Learning Hypothesis
March 4, 2025 at 11:03 AM
I provide the first empirical evidence supporting Shannon's (1945) Social Learning Hypothesis
Shannon argued that farmers often tried to follow the advice of a local agricultural society or successful farmers and "got worse crops than before". Their inability to rely on social learning compelled them to rely only on themselves, fostering their "traditional individualism."
March 4, 2025 at 11:03 AM
Shannon argued that farmers often tried to follow the advice of a local agricultural society or successful farmers and "got worse crops than before". Their inability to rely on social learning compelled them to rely only on themselves, fostering their "traditional individualism."
However, substantial local soil heterogeneity in certain areas implied that optimal farming practices were highly localized, thereby limiting the effectiveness of social learning. The American historian Fred Shannon argued in his 1945 book that this weakened communal ties
March 4, 2025 at 11:03 AM
However, substantial local soil heterogeneity in certain areas implied that optimal farming practices were highly localized, thereby limiting the effectiveness of social learning. The American historian Fred Shannon argued in his 1945 book that this weakened communal ties
One possible strategy was "learning by doing" (i.e. individual trial and error). Another and potentially more efficient strategy was to engage in social learning and to build on the experience of their neighbors
March 4, 2025 at 11:03 AM
One possible strategy was "learning by doing" (i.e. individual trial and error). Another and potentially more efficient strategy was to engage in social learning and to build on the experience of their neighbors