A Systematic Review of Propensity Score Methods in the Social Sciences

Abstract

The use of propensity scores in psychological and educational research has been steadily increasing in the last 2 to 3 years. However, there are some common misconceptions about the use of different estimation techniques and conditioning choices in the context of propensity score analysis. In addition, reporting practices for propensity score analyses often lack important details that allow other researchers to confidently judge the appropriateness of reported analyses and potentially to replicate published findings. In this article we conduct a systematic literature review of a large number of published articles in major areas of social science that used propensity scores up until the fall of 2009. We identify common errors in estimation, conditioning, and reporting of propensity score analyses and suggest possible solutions.

Notes

¹Another part of this assumption is that no propensity scores with the two extreme values of 0 and 1 are observed, or in other words each unit has a nonzero probability of being either assigned to the treatment or the control condition.

²The “other” category was introduced because counts in several categories were very low and reliability suffered when these categories were considered separately.