It is important to understand that Fisher and colleagues have not studied the effects of particular medical interventions on outcomes of care for patients with acute myocardial infarction, colorectal cancer, and hip fracture. Rather, they studied the outcomes of care for patients who lived in areas characterized by different medical styles and overall treatment intensities. Thus, their results do not show whether any specific treatment protocols are more or less effective. Rather, their study illuminates the question of whether reducing intensity of medical treatment overall would likely have important effects on patient outcomes. If their natural randomization is effective, then one can infer that patients in the areas with greater intensity gained little or no additional health (or, by Fisher and colleagues' estimates, had actually slightly worse health outcomes), at least for the index diseases studied. Of course, if the small-area variation approach did not achieve natural randomization, then drawing that inference would risk a possible ecologic fallacy.