<P> A major trend in employer sponsored cover has been increasing premiums, deductibles, and co-payments for medical services, and increasing the costs of using out - of - network health providers rather than in - network providers . </P> <P> Public insurance cover increased from 2000--2010 in part because of an aging population and an economic downturn in the latter part of the decade . Funding for Medicaid and CHIP expanded significantly under the 2010 health reform bill . The proportion of individuals covered by Medicaid increased from 10.5% in 2000 to 14.5% in 2010 and 20% in 2015 . The proportion covered by Medicare increased from 13.5% in 2000 to 15.9% in 2010, then decreased to 14% in 2015 . </P> <P> The uninsured proportion was stable at 14--15% from 1990 to 2008, then rose to a peak of 18% in Q3 2013 and rapidly fell to 11% in 2015 . The proportion without insurance has stabilized at 9% . </P> <P> A 2011 study found that there were 2.1 million hospital stays for uninsured patients, accounting for 4.4% ($17.1 billion) of total aggregate inpatient hospital costs in the United States . The costs of treating the uninsured must often be absorbed by providers as charity care, passed on to the insured via cost - shifting and higher health insurance premiums, or paid by taxpayers through higher taxes . </P>

The majority of u.s. employees with health coverage are enrolled in