The Information Basis of Matching with Propensity Score

This paper examines the foundations for comparing individuals and treatment subjects in experimental and other program evaluation contexts. We raise the question of multiattribute "characterization" of individuals both theoretically and statistically. The paper examines the information basis of characterizing individuals and offers alternatives motivated by welfare and decision theories. The proposed method helps place propensity scores and other "matching" proposals in context and reveals their advantages and disadvantages. We do not find the implied theoretical assumptions underlying propensity scores to be attractive or robust. Our proposal does not "solve" the matching problem, but provides bounds on inferences and makes clear the arbitrariness of specific solutions.