percent reduction in mortality for those with hypertension." Newhouse, summarizing the RAND HIE in 2004, wrote, "For most people enrolled in the RAND experiment, who were typical of Americans covered by employment-based insurance, the variation in use across the plans appeared to have minimal to no effects on health status. By contrast, for those who were both poor and sick -- people who might be found among those covered by Medicaid or lacking insurance -- the reduction in use was harmful, on average." Criticisms and legacy The RAND Health Insurance Experiment is considered "one of the best experimental social science studies ever conducted". However, several criticisms of the study have been suggested. Some authors questioned the generalizability of comparisons of HMO and FFS care since data on the former were based on a "single, relatively small but well-managed" HMO in Seattle. One 2007 article suggested that the "large number of participants who voluntarily dropped out of the costsharing arms of the experiment" could have invalidated the RAND HIE's findings. In response, Newhouse and colleagues described the argument as "implausible". The RAND HIE did not study people without health insurance and so could not determine how the presence or absence of health insurance affects health. Nevertheless, the study opened the way for increased cost sharing for medical care in the 1980s and 1990s. The RAND HIE is still referenced in the academic literature as a "gold standard" study in research on the effects of health insurance. For example, in 2007 RAND researchers reviewed the literature published between 1985 and 2006 on prescription drug cost sharing, which included co-payments, tiering, coinsurance, pharmacy benefit caps or monthly prescription limits, formulary restrictions, and reference pricing. In summarizing 132 articles, they found that the RAND HIE provided the only relevant experimental data; all other studies they reviewed were observational. They concluded: Increased cost sharing is associated with lower rates of drug treatment, worse adherence among existing users, and more frequent discontinuation of therapy. For each 10% increase in cost sharing, prescription drug spending decreases by 2% to 6%, depending on class of drug and condition of the patient. The reduction in use associated with a benefit cap, which limits either the coverage amount or the number of covered prescriptions, is consistent with other cost-sharing features. For some chronic conditions, higher cost sharing is associated with increased use of medical services, at least for patients with