title: Near/far matching: a study design approach to instrumental variables.
abstract: Classic instrumental variable techniques involve the use of structural equation modeling or other forms of parameterized modeling. In this paper we use a nonparametric, matching-based instrumental variable methodology that is based on a study design approach. Similar to propensity score matching, though unlike classic instrumental variable approaches, near/far matching is capable of estimating causal effects when the outcome is not continuous. Unlike propensity score matching, though similar to instrumental variable techniques, near/far matching is also capable of estimating causal effects even when unmeasured covariates produce selection bias. We illustrate near/far matching by using Medicare data to compare the effectiveness of carotid arterial stents with cerebral protection versus carotid endarterectomy for the treatment of carotid stenosis.
authors.affiliation: Department of Statistics, Stanford University, 390 Serra Mall, Stanford, CA 94305, USA.
authors.forename: Mike
authors.initials: M
authors.lastname: Baiocchi
authors.affiliation: Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA, USA. Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Dylan S
authors.initials: DS
authors.lastname: Small
authors.affiliation: Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Yang
authors.affiliation: Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA, USA. Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Polsky
authors.affiliation: Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, PA, USA. Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. Department of Veterans Affairs' Center for Health Equity Research and Promotion, Philadelphia Veterans Affairs Medical Center, Philadelphia, PA, USA.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Groeneveld
keywords: Binary outcomes; Comparative effectiveness; Instrumental variables; Matching; Medicare data; Study design