The Commonwealth Fund Health Insurance Tracking Survey of Young Adults finds that between November 2010 and November 2011, an estimated 13.7 million young adults ages 19–25 stayed on or joined their parents' health plans, including 6.6 million who likely would not have been able to do so prior to the passage of the Affordable Care Act. The findings of the survey underscore the need for policymakers to implement the remaining coverage expansions in the law. Nearly two of five young adults ages 19–29 were without health insurance for all or part of 2011, with young adults in low- and moderate-income households the most at risk.