世界経済・社会統計 = World development indicators

This paper investigates the role of social learning in the diffusion of a new agri cultural technology in Ghana. We use unique data on farmers' communication patterns to define each individual's information neighborhood. Conditional on many potentially confounding variables, we find evidence that farmers adjust their inputs to align with those of their information neighbors who were surpris ingly successful in previous periods. The relationship of these input adjustments to experience further indicates the presence of social learning. In addition, applying the same method to input choices for another crop, of known technol ogy, correctly indicates an absence of social learning effects. (JEL D83, 013, 033, Q16)

/pdf/learning-about-a-new-technology-pineapple-in-ghana-3vxvkgahoh.pdf

Learning About a New Technology: Pineapple in Ghana

This essay reviews progress in empirical economics since Leamer's (1983) critique. Leamer highlighted the benefits of sensitivity analysis, a procedure in which researchers show how their results change with changes in specification or functional form. Sensitivity analysis has had a salutary but not a revolutionary effect on econometric practice. As we see it, the credibility revolution in empirical work can be traced to the rise of a design-based approach that emphasizes the identification of causal effects. Design-based studies typically feature either real or natural experiments and are distinguished by their prima facie credibility and by the attention investigators devote to making the case for a causal interpretation of the findings their designs generate. Design-based studies are most often found in the microeconomic fields of Development, Education, Environment, Labor, Health, and Public Finance, but are still rare in Industrial Organization and Macroeconomics. We explain why IO and Macro would do well to embrace a design-based approach. Finally, we respond to the charge that the design-based revolution has overreached.

The Credibility Revolution in Empirical Economics: How Better Research Design is Taking the Con out of Econometrics

We study peer effects in the workplace. Specifically, we investigate whether, how, and why the productivity of a worker depends on the productivity of coworkers in the same team. Using high-frequency data on worker productivity from a large supermarket chain, we find strong evidence of positive productiv ity spillovers from the introduction of highly productive personnel into a shift. Worker effort is positively related to the productivity of workers who see him, but not workers who do not see him. Additionally, workers respond more to the presence of coworkers with whom they frequently interact. We conclude that social pressure can partially internalize free-riding externalities that are built into many workplaces. (JEL J24, L81, M54)

https://www.econstor.eu/bitstream/10419/33749/1/530032856.pdf

Peers at Work

We use policy discontinuities at state borders to identify the effects of minimum wages on earnings and employment in restaurants and other low-wage sectors. Our approach generalizes the case study method by considering all local differences in minimum wage policies between 1990 and 2006. We compare all contiguous county pairs in the United States that straddle a state border and find no adverse employment effects. We show that traditional approaches that do not account for local economic conditions tend to produce spurious negative effects due to spatial heterogeneities in employment trends that are unrelated to minimum wage policies. Our findings are robust to allowing for long-term effects of minimum wage changes.

/pdf/minimum-wage-effects-across-state-borders-estimates-using-2q9jkegquz.pdf

Minimum Wage Effects Across State Borders: Estimates Using Contiguous Counties

Internet review forums increasingly supplement expert opinion and social networks in informing consumers about product quality. However, limited empirical evidence links digital word-of-mouth to purchasing decisions. We implement a regression discontinuity design to estimate the effect of positive Yelp.com ratings on restaurant reservation availability. An extra half-star rating causes restaurants to sell out 19 percentage points (49%) more frequently, with larger impacts when alternate information is more scarce. These returns suggest that restaurateurs face incentives to leave fake reviews but a rich set of robustness checks confirm that restaurants do not manipulate ratings in a confounding, discontinuous manner.

/pdf/learning-from-the-crowd-regression-discontinuity-estimates-3f6xo0sn4o.pdf

Learning from the Crowd: Regression Discontinuity Estimates of the Effects of an Online Review Database*

We use recruitment into a laboratory experiment in Kolkata, India to analyze how job networks select individuals for employment opportunities. We present evidence that individuals face a tradeoff between choosing the most qualified individual for the job and the individual who is ideal from the perspective of their social network. The experiment allows randomly selected subjects to refer members of their social networks to subsequent rounds of the experiment and varies the incentive schemes offered to these participants. We find that when faced with performance pay, individuals are more likely to refer co-workers and less likely to refer family members. High ability participants who are offered performance pay recruit referrals who perform significantly better on a cognitive ability task and also prove to be more reliable as evidenced by their choices in the trust game and performance on an effort task.

/pdf/who-gets-the-job-referral-evidence-from-a-social-networks-llxvexmjk9.pdf

Who Gets the Job Referral? Evidence from a Social Networks Experiment

In order to induce farmers to adopt a productive new agricultural technology, we apply simple and complex contagion diffusion models on rich social network data from 200 villages in Malawi to identify seed farmers to target and train on the new technology. A randomized controlled trial compares these theory-driven network targeting approaches to simpler strategies that either rely on a government extension worker or an easily measurable proxy for the social network (geographic distance between households) to identify seed farmers. Our results indicate that technology diffusion is characterized by a complex contagion learning environment in which most farmers need to learn from multiple people before they adopt themselves. Network theory based targeting can out-perform traditional approaches to extension, and we identify methods to realize these gains at low cost to policymakers. 
Keywords: Social Learning, Agricultural Technology Adoption, Complex Contagion, Malawi 
JEL Classification Codes: O16, O13

Can Network Theory-based Targeting Increase Technology Adoption?

Using a eld experiment in Malawi where men and women apply for future surveyor positions with a local rm, we nd that highly skilled women are systematically disadvantaged through the use of referrals. This happens both because most men recommend other men, and because women refer fewer candidates who qualify for the position. We document that segregated networks do not cause this behavior. We develop a theoretical model of referral choice and exploit random variation in referral contract terms to nd that that both men’s and women’s biases result from social incentives rather than expectations of performance. We also document that the screening potential of networks is maximized when men refer men. This paper suggests that the use of social networks in hiring is an additional channel through which women are disadvantaged in the labor market.

/pdf/do-job-networks-disadvantage-women-evidence-from-a-1zf4rul0dj.pdf

Do Job Networks Disadvantage Women? Evidence from a Recruitment Experiment in Malawi

This paper examines the importance of network-based intergen erational correlations in South Africa. I use longitudinal data on young South Africans to examine the covariance of children's employment with the usefulness of parents in their job search. I find that fathers serve as useful network connections to their sons {not daughters), and that mothers do not seem to be useful network con nections. The father-son effect is robust to alternate explanations of specific human capital and correlated networks. The size of this effect is large. Present fathers' utility as network connections may be responsible for a one-third increase in their sons' employment rates. (JEL D31, J12, J13, J24, J62, 015, Z13)

/pdf/intergenerational-networks-unemployment-and-persistent-4047yc43vk.pdf

Jeremy Magruder

Papers

Learning from the Crowd: Regression Discontinuity Estimates of the Effects of an Online Review Database*

Who Gets the Job Referral? Evidence from a Social Networks Experiment

Can Network Theory-based Targeting Increase Technology Adoption?

Do Job Networks Disadvantage Women? Evidence from a Recruitment Experiment in Malawi

Intergenerational Networks, Unemployment, and Persistent Inequality in South Africa