Fletcher Jason M, Ross Stephen L
La Follette School of Public Affairs, Departments of Sociology, Agricultural and Applied Economics, and Population Health Sciences, University of Wisconsin-Madison, Madison, WI, USA.
Department of Economics, University of Connecticut, Storrs, CT, USA.
Health Econ. 2018 Oct;27(10):1450-1483. doi: 10.1002/hec.3780. Epub 2018 Jun 6.
This paper estimates the effects of friends' smoking and drinking on own behavior while controlling for correlated unobservables between friends. The effect of friends' behaviors is identified by comparing similar individuals who have similar friendship opportunities and make similar friendship choices, exploiting the idea that friendship choice reveals information about unobservables. We combine this identification strategy with an across-cohort within school design so that identification arises in our reduced form estimates from across-grade differences in the clustering of health behaviors. Finally, we use estimated information on correlated unobservables to examine longitudinal data on the onset of health behaviors, where the likelihood of reverse causality should be minimal. We find evidence that this strategy produces somewhat smaller (no more than 16% smaller) friendship effect estimates than the more standard school fixed effect models consistent with at most modest bias from correlated unobservables.
本文在控制朋友间相关不可观测因素的同时，估计朋友吸烟和饮酒对自身行为的影响。通过比较拥有相似交友机会并做出相似交友选择的相似个体，利用友谊选择揭示不可观测因素信息这一理念，来识别朋友行为的影响。我们将这种识别策略与学校内跨队列设计相结合，以便在我们的简化形式估计中，从健康行为聚类的年级差异中产生识别。最后，我们使用关于相关不可观测因素的估计信息来检验健康行为开始的纵向数据，在这些数据中反向因果关系的可能性应最小。我们发现，与来自相关不可观测因素的至多适度偏差相一致的更标准的学校固定效应模型相比，该策略产生的友谊效应估计值略小（不超过16%）。
