Dias, Monica Costa; Ichimura, Hidehiko; Berg, Gerard J. … - In: Journal of the American Statistical Association 108 (2013) 502, pp. 441-455
Matching methods for treatment evaluation based on a conditional independence assumption do not balance selective unobserved differences between treated and nontreated. We derive a simple correction term if there is an instrument that shifts the treatment probability to zero in specific cases....