The percentage of uninsured adults in 2009-2011 was lowest (25% of adults aged 18-34 years and 13% of those aged 35-64 years) among those residing in large fringe metropolitan counties (suburbs of large cities). Among adults aged 18-34 years,the percentage uninsured was highest in the most rural counties (35%) and ranged from 28% to 31% in other urbanization levels. Among adults aged 35-64 years, 17%-18% in medium and small metropolitan areas and 20%-22% in large central metropolitan and nonmetropolitan counties lacked insurance. For all urbanization levels, or the percentage uninsured was lower for adults aged 35-64 years than for younger adults.
Source: cdc.gov