Large numbers of Americans continue to experience gaps in health coverage, even during times of economic growth, according to a new Commonwealth Fund–supported study published by Medical Care Research and Review. Researchers found that some 89 million people ages 4 to 64 were uninsured for at least one month from 2004 to 2007. The new analysis, the authors say, will establish a baseline to help policymakers evaluate the effects of reform on coverage stability for the estimated 30 million Americans expected to gain coverage through the Affordable Care Act.