While Medicare provides essential coverage to seniors and people with disabilities, there are no limits on out-of-pocket costs. One of four Medicare beneficiaries, or 11.5 million people, were underinsured in 2013–14, meaning they spent a high share of income on medical costs, according to a new brief based on U.S. Census surveys by Cathy Schoen, a 2016 senior scholar in residence at the New York Academy of Medicine, and colleagues.