A key idea in the great health reform debate of 2009 is that uninsurance and the high costs of medical care are linked. Covering uninsured patients will improve their health over time, goes the claim, which in turn will offset some of the costs of providing insurance to these patients. This is almost certainly true. The debate is over the magnitude of the offset savings. In their provocative article in this issue, McWilliams and colleagues (1) estimated the size of the offset by using the concrete example of the link between uninsurance among near-elderly adults and future Medicare expenditures. Their work addresses a problem of great policy and scientific interest. The strength of this link matters in the policy setting because the high cost of health reform is a central impediment to legislative action, and it matters in the scientific setting because establishing the link between uninsurance and health in a statistically meaningful way has been difficult. The only randomized experiment on the topic-the RAND Health Insurance Experiment-found that even after 5 years, mortality rates and overall health status were essentially the same for people assigned free insurance as for people assigned much less generous insurance