Today I had the opportunity to testify before the Senate Budget Committee about CBO’s most recent analysis of the long-term budget outlook.

Under current law, the federal budget is on an unsustainable path, because federal debt will continue to grow much faster than the economy over the long run. Although great uncertainty surrounds long-term fiscal projections, rising costs for health care and the aging of the population will cause federal spending to increase rapidly under any plausible scenario for current law. Unless revenues increase just as rapidly, the rise in spending will produce growing budget deficits. Large budget deficits would reduce national saving, leading to more borrowing from abroad and less domestic investment, which in turn would depress economic growth in the United States. Over time, accumulating debt would cause substantial harm to the economy. The following chart shows our projection of federal debt relative to GDP under the two scenarios we modeled.

Federal Debt Held by the Public Under CBO’s Long-Term Budget Scenarios (Percentage of GDP)

Keeping deficits and debt from reaching these levels would require increasing revenues significantly as a share of GDP, decreasing projected spending sharply, or some combination of the two.

Measured relative to GDP, almost all of the projected growth in federal spending other than interest payments on the debt stems from the three largest entitlement programs—Medicare, Medicaid, and Social Security. For decades, spending on Medicare and Medicaid has been growing faster than the economy. CBO projects that if current laws do not change, federal spending on Medicare and Medicaid combined will grow from roughly 5 percent of GDP today to almost 10 percent by 2035. By 2080, the government would be spending almost as much, as a share of the economy, on just its two major health care programs as it has spent on all of its programs and services in recent years.

In CBO’s estimates, the increase in spending for Medicare and Medicaid will account for 80 percent of spending increases for the three entitlement programs between now and 2035 and 90 percent of spending growth between now and 2080. Thus, reducing overall government spending relative to what would occur under current fiscal policy would require fundamental changes in the trajectory of federal health spending. Slowing the growth rate of outlays for Medicare and Medicaid is the central long-term challenge for fiscal policy.

Under current law, spending on Social Security is also projected to rise over time as a share of GDP, but much less sharply. CBO projects that Social Security spending will increase from less than 5 percent of GDP today to about 6 percent in 2035 and then roughly stabilize at that level. Meanwhile, as depicted below, government spending on all activities other than Medicare, Medicaid, Social Security, and interest on federal debt—a broad category that includes national defense and a wide variety of domestic programs—is projected to decline or stay roughly stable as a share of GDP in future decades.

Spending Other Than That for Medicare, Medicaid, Social Security, and Net Interest, 1962 to 2080 (Percentage of GDP)

Federal spending on Medicare, Medicaid, and Social Security will grow relative to the economy both because health care spending per beneficiary is projected to increase and because the population is aging. As shown in the figure below, between now and 2035, aging is projected to make the larger contribution to the growth of spending for those three programs as a share of GDP. After 2035, continued increases in health care spending per beneficiary are projected to dominate the growth in spending for the three programs.

Factors Explaining Future Federal Spending on Medicare, Medicaid, and Social Security (Percentage of GDP)

The current recession and policy responses have little effect on long-term projections of noninterest spending and revenues. But CBO estimates that in fiscal years 2009 and 2010, the federal government will record its largest budget deficits as a share of GDP since shortly after World War II. As a result of those deficits, federal debt held by the public will soar from 41 percent of GDP at the end of fiscal year 2008 to 60 percent at the end of fiscal year 2010. This higher debt results in permanently higher spending to pay interest on that debt. Federal interest payments already amount to more than 1 percent of GDP; unless current law changes, that share would rise to 2.5 percent by 2020.

(This was originally posted at the CBO Director's blog)