Recruitment needs vs clinical trial participation rates at 1%, 3%, 5%, and 10% reflected by the green, yellow, gray, and red bars, respectively. This graph represents trials that accrued in the United States, internationally, and in the United States + internationally (A); in the United States and/or the United States + internationally (B); or in the United States only (C). The period reflects trials that were completed and/or enrolling between 2000 and 2017.