With limited money to spend on the Oregon Health Plan in 2008, state officials decided the fairest way to enroll additional people would be a random lottery. More than 85,000 people put their names in the list. Only 10,000 gained coverage in Oregon's Medicaid program for low-income residents. The chain of events inadvertently set the stage for an unprecedented experiment – the equivalent of a randomized clinical trial measuring how health insurance changes the lives of people who gain coverage. "It's provided the ideal experiment to really understand cause and effect," said Heidi Allen, a research scientist with Providence Health & Services in Portland. After one year, the experiment shows that gaining coverage makes an immediate difference in personal health and financial security. The newly insured, compared to their uninsured peers, were more likely to receive preventive services and to establish long-lasting ties to a trusted doctor.