就是第三列里面规模最接近的。

这么简单的工作，用不着PSM吧，PSM的优势在于从多个维度寻找配对公司。

你这个问题只需要根据0/1变量和SIZE变量分组排序即可，排序相近的不就是规模相当的公司吗。

[此贴子已经被作者于2009-3-30 16:22:57编辑过]

请参考：

Becker, S., A. Ichino, 2002, Estimation of average treatment effects based on propensity scores, The Stata Journal, 2 (4): 358-377.

Abadie, A., G. Imbens, 2002, Simple and Bias-Corrected Matching Estimators for Average for Average Treatment Effects in STATA, The Stata Journal, 1 (1): 1-18.

Abadie, A., D. Herr, J. Imbens, 2001, Implementing Matching Estimators for Average Treatment Effects in Stata, The Stata Journal, 1: 1-18.

Abadie, A., D. Drukker, J. Herr, G. Imbens, 2004, Implementing matching estimators for average treatment effects in Stata, The Stata Journal, 4: 290-311.

Caliendo, M., S. Kopeinig, 2008, Some practical guidance for the implementation of propensity score matching, Journal of Economic Surveys, 22 (1): 31-72.