Case Study 2 — The U.S. National Debt: How Much Is Too Much?

As of 2025, the U.S. national debt exceeds $36 trillion — about 125% of GDP. Annual interest payments on the debt exceed $1 trillion — more than the defense budget. The deficit (annual borrowing) is about $2 trillion per year.

These numbers sound alarming. But are they? This case study applies the loanable funds framework and the crowding-out analysis from §28.2 to evaluate whether the U.S. debt is a crisis, a concern, or a manageable situation.

The facts

Debt-to-GDP ratio: the most meaningful measure. The U.S. debt-to-GDP ratio was about 35% in 1980, rose to about 65% by 2007, jumped to about 100% after the 2008 crisis and stimulus, and rose further to 125% after the COVID fiscal response.

Interest burden: total interest payments were about $350B/year in 2019 and have risen to over $1T/year in 2025, driven by both higher debt and higher interest rates (the 2022–23 rate hikes increased the government's borrowing cost).

Who holds the debt: about 30% is held by foreign governments and investors (China, Japan, others). About 25% is held by the Federal Reserve (from QE). About 45% is held by U.S. domestic investors (pension funds, mutual funds, insurance companies, individuals).

The "debt is a crisis" view

Crowding out. Large government borrowing raises interest rates and displaces private investment. With the government borrowing $2T/year, less capital is available for business investment, potentially reducing long-run growth.

Interest expense. As interest payments consume a growing share of the federal budget (now about 15% and rising), less money is available for other spending (defense, infrastructure, education, healthcare). At some point, interest payments could crowd out essential government functions.

Loss of fiscal flexibility. If a future crisis requires large fiscal stimulus (another pandemic, a financial crisis, a war), the government's ability to borrow might be constrained if the debt is already very high.

Bond market confidence. If investors lose confidence in the government's ability to manage its debt, they may demand higher interest rates (a "bond vigilante" scenario), which raises borrowing costs, increases the deficit, raises the debt further — a potential spiral.

The "debt is manageable" view

The U.S. is not Greece. The U.S. borrows in its own currency (dollars), which it can print. Countries that borrow in foreign currencies (Greece borrowed in euros it couldn't print) face a hard constraint; the U.S. does not. The U.S. can always pay its debts by printing money — though doing so would be inflationary if taken too far.

Interest rates are low in historical context. Despite the 2022–23 rate hikes, real interest rates on long-term government debt remain relatively low (about 1.5–2.5% in real terms as of 2025). If the real interest rate is below the real growth rate of GDP (r < g — the Piketty condition from Chapter 13, applied to government debt), the debt-to-GDP ratio stabilizes or declines even without a balanced budget.

The debt finances real things. Not all government borrowing is wasteful. The COVID fiscal response prevented a depression. Infrastructure investment (roads, bridges, broadband) raises future productivity. Education spending raises future human capital. The relevant question is not "is the government borrowing?" but "is the government spending the borrowed money on things that are worth it?"

Japan. Japan's debt-to-GDP ratio is about 260% — double the U.S.'s. Japan has not experienced a debt crisis. Interest rates in Japan remain very low. The Japanese example suggests that very high debt-to-GDP ratios can be sustained for decades without crisis — at least in countries that borrow in their own currency and have stable institutions.

The honest assessment

The U.S. national debt is a concern but not (yet) a crisis. The path is unsustainable in the very long run — debt can't grow faster than GDP forever. But the timing and severity of any reckoning depend on: - Future interest rates (higher rates = larger interest burden) - Future economic growth (faster growth = debt more manageable) - Future fiscal policy (whether Congress acts to reduce deficits) - Investor confidence (whether bond markets continue to lend at reasonable rates)

Most economists agree that the U.S. should put the debt on a more sustainable path — gradually, through some combination of spending restraint and revenue increases. Most also agree that dramatic austerity (sharp spending cuts or tax hikes during a weak economy) would be counterproductive.

The loanable funds framework tells you: government borrowing has costs (crowding out, interest burden). The macro framework tells you: those costs depend on conditions. The political framework tells you: deficit reduction is extremely hard because every spending cut and every tax increase has losers who organize against it.

Discussion questions

1. Is the U.S. national debt a crisis, a concern, or a non-issue? Apply the loanable funds framework.
2. Japan has a 260% debt-to-GDP ratio and no crisis. Does this mean debt levels don't matter?
3. The 2022–23 rate hikes increased the government's interest burden by hundreds of billions. Should the Fed have considered the fiscal impact when setting rates?
4. "Every dollar of debt is a dollar of future taxes." Is this true? Does it matter?
5. If you were in Congress, how would you reduce the deficit? Which spending would you cut? Which taxes would you raise?