From The Congressional Budget Office, Director Douglas Elmendorf's testimony, "Testimony: The Budget and Economic Outlook: Fiscal Years 2013 to 2023" before the US Senate Committee on the Budget, February 12, 2013:
In CBO’s baseline projections, deficits continue to shrink over the next few years, falling to 2.4 percent of GDP by 2015. Deficits are projected to increase later in the coming decade, however, because of the pressures of an aging population, rising health care costs, an expansion of federal subsidies for health insurance, and growing interest payments on federal debt. As a result, federal debt held by the public is projected to remain historically high relative to the size of the economy for the next decade. By 2023, if current laws remain in place, debt will equal 77 percent of GDP and be on an upward path, CBO projects (see Figure 1).
Such high and rising debt would have serious negative consequences: When interest rates rose to more normal levels, federal spending on interest payments would increase substantially. Moreover, because federal borrowing reduces national saving, the capital stock would be smaller and total wages would be lower than they would be if the debt was reduced. In addition, lawmakers would have less flexibility than they might ordinarily to use tax and spending policies to respond to unexpected challenges. Finally, such a large debt would increase the risk of a fiscal crisis, during which investors would lose so much confidence in the government’s ability to manage its budget that the government would be unable to borrow at affordable rates.
***Budgetary outcomes will also be affected by decisions about whether to continue certain policies that have been in effect in recent years. Such policies could be continued, for example, by extending some tax provisions that are scheduled to expire (and that have routinely been extended in the past) or by preventing the 25 percent cut in Medicare’s payment rates for physicians that is due to occur in 2014. If, for instance, lawmakers eliminated the automatic spending cuts scheduled to take effect in March (but left in place the original caps on discretionary funding set by the Budget Control Act), prevented the sharp reduction in Medicare’s payment rates for physicians, and extended the tax provisions that are scheduled to expire at the end of calendar year 2013 (or, in some cases, in later years), budget deficits would be substantially larger over the coming decade than in CBO’s baseline projections. With those changes, and no offsetting reductions in deficits, debt held by the public would rise to 87 percent of GDP by the end of 2023 rather than to 77 percent.
In addition to those decisions, lawmakers will continue to face the longer-term budgetary issues posed by the substantial federal debt and by the implications of rising health care costs and the aging of the population.
CBO Testimony the Budget and Economic Outlook 2013 to 2023 by