“…In addition, absolute or relative distance has been used as an instrumental variable (IV) in analyses of other outcomes. Distance strongly predicts choice of provider in various clinical contexts (McClellan, McNeil, and Newhouse 1994;Zwanziger, Mukamel, and Indridason 2002;Hirth et al 2003Hirth et al , 2014Brooks et al 2006;Shugarman and Brown 2006;Grabowski et al 2013). In the dialysis context, Brooks et al (2006) found the relative proximity to for-profit and nonprofit dialysis facilities to be the strongest predictor of the type of facility chosen, and that use of this measure as an IV eliminated the relationship between ownership and patient survival that existed in observational data.…”