Non-classical measurement error in instrumental variables estimation: An application to the medical care costs of obesity

IF 2 3区 医学 Q2 ECONOMICS
Health economics Pub Date : 2024-07-18 DOI:10.1002/hec.4882
Adam I. Biener, Chad Meyerhoefer, John Cawley
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引用次数: 0

Abstract

Estimates of the impact of body mass index and obesity on health and labor market outcomes often use instrumental variables estimation (IV) to mitigate bias due to endogeneity. When these studies rely on survey data that include self- or proxy-reported height and weight, there is non-classical measurement error due to the tendency of individuals to under-report their own weight. Mean reverting errors in weight do not cause IV to be asymptotically biased per se, but may result in bias if instruments are correlated with additive error in weight. We demonstrate the conditions under which IV is biased when there is non-classical measurement error and derive bounds for this bias conditional on instrument strength and the severity of mean-reverting error. We show that improvements in instrument relevance alone cannot eliminate IV bias, but reducing the correlation between weight and reporting error mitigates the bias. A solution we consider is regression calibration (RC) of endogenous variables with external validation data. In simulations, we find IV estimation paired with RC can produce consistent estimates when correctly specified. Even when RC fails to match the covariance structure of reporting error, there is still a reduction in asymptotic bias.

工具变量估计中的非经典测量误差:肥胖症医疗成本的应用。
在估算体重指数和肥胖对健康和劳动力市场结果的影响时,通常会使用工具变量估算(IV)来减轻内生性带来的偏差。当这些研究依赖于包括自我或委托人报告的身高和体重的调查数据时,由于个人倾向于低报自己的体重,因此存在非经典性测量误差。体重的均值回归误差本身不会导致 IV 出现渐近偏差,但如果工具与体重的加性误差相关,则可能导致偏差。我们证明了当存在非经典测量误差时 IV 存在偏差的条件,并推导出了这种偏差在工具强度和均值回复误差严重程度条件下的界限。我们表明,仅靠提高工具相关性并不能消除 IV 偏差,但降低权重与报告误差之间的相关性可以减轻偏差。我们考虑的一个解决方案是利用外部验证数据对内生变量进行回归校准(RC)。在模拟中,我们发现与 RC 配对的 IV 估计在指定正确的情况下可以产生一致的估计值。即使 RC 无法与报告误差的协方差结构相匹配,渐近偏差仍会减少。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Health economics
Health economics 医学-卫生保健
CiteScore
3.60
自引率
4.80%
发文量
177
审稿时长
4-8 weeks
期刊介绍: This Journal publishes articles on all aspects of health economics: theoretical contributions, empirical studies and analyses of health policy from the economic perspective. Its scope includes the determinants of health and its definition and valuation, as well as the demand for and supply of health care; planning and market mechanisms; micro-economic evaluation of individual procedures and treatments; and evaluation of the performance of health care systems. Contributions should typically be original and innovative. As a rule, the Journal does not include routine applications of cost-effectiveness analysis, discrete choice experiments and costing analyses. Editorials are regular features, these should be concise and topical. Occasionally commissioned reviews are published and special issues bring together contributions on a single topic. Health Economics Letters facilitate rapid exchange of views on topical issues. Contributions related to problems in both developed and developing countries are welcome.
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