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标题：Impact of the Density Support on the Matching Bias: A Matched-Pair Analysis Based on Business Survey Data
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作者：Laurent Donzé
期刊名称：KOF Working Papers
出版年度：2005
卷号：1
出版社：KOF Konjunkturforschungsstelle, ETH Zürich
摘要：Matching methods have been extensively used to evaluate economic policy. However, they are not without fault and, indeed, a selection bias may appear. In 1998, Heckman and al. (1998) have precisely characterize this bias by a decomposition in three parts which can be non parametrically estimated. These estimations depend among others on the support of the conditional density function of the covariates X used for the matching. In a study of the impact of the policy of supporting the adoption of advanced manufac- turing technologies by Swiss rms, we have measured the di erent components of the bias. We put into evidence the extreme sensibility of the results to the measure of support density.