The success of large-scale COVID-19 vaccination campaigns is contingent upon people being willing to receive the vaccine. Our study explored COVID-19 vaccine hesitancy and its correlates in eight different countries around the globe. We analyzed convenience sample data collected between March 2020 and January 2021 as part of the iCARE cross-sectional study. Univariate and multivariate statistical analyses were conducted to explore the correlates of vaccine hesitancy. We included 32,028 participants from eight countries, and observed that 27% of the participants exhibited vaccine hesitancy, with increases over time. France reported the highest level of hesitancy (47.3%) and Brazil reported the lowest (9.6%). Women, younger individuals (≤29 years), people living in rural areas, and those with a lower perceived income were more likely to be hesitant. People who previously received an influenza vaccine were 70% less likely to report COVID-19 vaccine hesitancy. We observed that people reporting greater COVID-19 health concerns were less likely to be hesitant, whereas people with higher personal financial concerns were more likely to be hesitant. Our findings indicate that there is substantial vaccine hesitancy in several countries, with cross-national differences in the magnitude and direction of the trend. Vaccination communication initiatives should target hesitant individuals (women, younger adults, people with lower incomes and those living in rural areas), and should highlight the immediate health, social and economic benefits of vaccination across these settings. Country-level analyses are warranted to understand the complex psychological, socio-environmental, and cultural factors associated with vaccine hesitancy.

Homophily, or the fact that similar individuals tend to interact with each other, is a prominent feature of economic and social networks. I show that the equilibrium structure of homophily has empirical power. I build a strategic model of network formation, which produces a unique equilibrium network. Individuals have homophilic preferences and face capacity constraints on the number of links. I develop a novel empirical method, based on the shape of the equilibrium network, which allows for the identification and estimation of the underlying homophilic preferences. I apply this new methodology to the formation of friendship networks.JEL Codes: D85,C72,C13 * Manuscript

Abstract:I present a model of conformism in social networks that incorporates both peer effects and self-selection. I find that equilibrium behaviors are linked through the Laplacian matrix of the equilibrium network. I show that conformism has positive social value and that social welfare can be bounded by network centrality and connectivity measures. I apply the model using empirical data on high school student participation in extracurricular activities. I find that the local effects of conformism (i.e. endogenous peer effect for a fixed network structure) range from 7.5% to 45%, depending on the number of peers that an individual has. Simulations show that the optimal policies of an inequality-averse policy-maker change in relation to the size of a school. Small schools should encourage shy students to integrate more with other students, while large schools should focus on promoting role models within the school.

SUMMARY We provide the first empirical application of a new approach proposed by Lee (Journal of Econometrics 2007; 140(2), 333–374) to estimate peer effects in a linear‐in‐means model when individuals interact in groups. Assumingsufficient group size variation, this approach allows to control for correlated effects at the group level and to solve the simultaneity (reflection) problem. We clarify the intuition behind identification of peer effects in the model. We investigate peer effects in student achievement in French, Science, Mathematics and History in secondary schools in the Province of Québec (Canada). We estimate the model using conditional maximum likelihood and instrumental variables methods. We find some evidence of peer effects. The endogenous peer effect is large and significant in Mathematics but imprecisely estimated in the other subjects. Some contextual peer effects are also significant. In particular, for most subjects, the average age of peers has a negative effect on own test score. Using calibrated Monte Carlo simulations, we find that high dispersion in group sizes helps with potential issues of weak identification. Copyright © 2012 John Wiley & Sons, Ltd.