“Federal debt held by the public will reach about $12.8 trillion by the end of this fiscal year, an amount that equals 74 percent of the nation’s total output (gross domestic product, or GDP) this year. If current laws generally remained unchanged—the assumption that underlies CBO’s baseline projections—CBO projects that such debt would climb to $20.6 trillion, or 77 percent of GDP, in 2024. Interest payments on that debt represent a large and rapidly growing expense of the federal government. CBO’s baseline shows net interest payments more than tripling under current law, climbing from $231 billion in 2014, or 1.3 percent of GDP, to $799 billion in 2024, or 3.0 percent of GDP—the highest ratio since 1996. The rising debt accounts for some of that increase, but much of it stems from CBO’s expectation that—largely owing to the improving economy—the average interest rate paid on that debt will more than double over the next 10 years, from 1.8 percent in 2014 to 3.9 percent in 2024. (Although interest rates are projected to rise sharply, CBO’s current projections of those rates are lower than its projections earlier in the year, reflecting the agency’s reassessment of the factors influencing real interest rates.) This blog post highlights some of the discussion about federal interest costs in An Update to the Budget and Economic Outlook: 2014 to 2024, which CBO released last week.”