During 2009, Medicare spent $11.7 billion for medical imaging, such as CT scans and MRI's. From 2005 to 2009, usage of scans grew at an annual rate of 14%, but may have slowed since due to a combination of changing incentives and saturation of usage. Initially, demanding patients insisted on scans; doctors feared malpractice suits if they refused; and doctors and hospitals wanted to maximize revenues. One study indicated that changing incentives may have reduced cost growth. From 2006 to 2010, the share of workers with deductibles exceeding $1,000 grew from 10 percent to 27 percent. Increased out-of-pocket expenses have made patients and physicians more cost conscious. Further, a combination of prior notification, higher patient co-payments and restrained reimbursements may have contributed to slowing cost growth. International comparisons of healthcare have found that the United States spends more per-capita than other similarly developed nations but falls below similar countries in various health metrics, suggesting inefficiency and waste. In addition, the United States has significant underinsurance and significant impending unfunded liabilities from its aging demographic and its social insurance programs Medicare and Medicaid (Medicaid provides free long-term care to the elderly poor). The fiscal and human impact of these issues have motivated reform proposals. According to 2009 World Bank statistics, the U.S. had the highest healthcare costs relative to the size of the economy (GDP) in the world, even though estimated 50.2 million citizens (approximately 15.6% of the September 2011 estimated population of 312 million) lacked insurance. In March 2010, billionaire Warren Buffett commented that the high costs paid by U.S. companies for their employees' health care put them at a competitive disadvantage. Further, an estimated 77 million Baby Boomers are reaching retirement age, which combined with significant annual increases in healthcare costs per person will place enormous budgetary strain on U.S. state and federal governments, particularly through Medicare and Medicaid spending (Medicaid provides long-term care for the elderly poor). Maintaining the long-term fiscal health of the U.S. federal government is significantly dependent on healthcare costs being controlled. In addition, the number of employers who offer health insurance has declined and costs for employer-paid health insurance are rising: from 2001 to 2007, premiums for family coverage increased 78%, while wages rose 19% and prices rose 17%, according to the Kaiser Family Foundation. Even for those who are employed, the private insurance in the US varies greatly in its coverage; one study by the Commonwealth Fund published in Health Affairs estimated that 16 million U.S. adults were underinsured in 2003.