Contrary to assumptions that undocumented immigrants contribute to emergency room crowding and drive up the cost of health care, healthcare utilization rates among the undocumented population in California are lower than or similar to those of other immigrants and U.S. citizens, a study by the UCLA Center for Health Policy Research finds. Based on 2009 California Health Interview Survey data, the report, Assessing Health Care Services Used by California's Undocumented Immigrant Population in 2010 (9 pages, PDF), found that undocumented and uninsured immigrants age 18 and older made fewer emergency room and doctor visits while using preventive health services at similar rates as other groups. Allowing undocumented immigrants to purchase insurance in the marketplaces under the Affordable Care Act, thus ensuring the receipt of low-cost preventive services, the report's authors argue, could contribute to lower premiums and reduce resource strains on safety-net providers in the state.