1 billion people, 15 percent of the world's population, are plagued by some type of disability. That's roughly one in seven. In the first report on the prevalence of disabilities since the 1970s, the World Health Organization and the World Bank predict this number will only go up as we get older. Though, NPR points out, "many countries don't collect numbers carefully, and definitions of disability differ from place to place...the World Bank/WHO folks sought out tabulations of people who have trouble seeing, hearing, walking, remembering, taking care of themselves or communicating." What they found was that depression is the most common debilitating ailment for people under 60, "followed by hearing and visual problems." According to the Center for Disease Control, in the United States alone, 35.6 million adults, i.e. 16 percent, have some kind of physical functioning difficulty.