Credibility, Not Just Pure Arithmetic: Horizon’s Framework for U.S. Debt Risk

The U.S. faces rising long-term debt risks, but a near-term sovereign crisis is unlikely because debt-service dynamics, productivity and institutional credibility matter more than debt size alone.

• Total U.S. government debt has exceeded $40 trillion, while the Congressional Budget Office projects publicly held debt at 120% of GDP by 2036, above the post-World War II peak.
• Horizon argues that net interest payments as a share of GDP are more informative than headline debt, noting that borrowing costs remained around current levels from the mid-1980s through the late 1990s and that growth exceeded interest rates during much of the post-war and post-2008 periods.
• U.S. credibility rests on institutional, monetary and political pillars; the authors view the first two as strong but identify debt-ceiling standoffs, Congressional dysfunction and threats to central-bank independence as political vulnerabilities.
• Sovereign crises typically require both weak debt dynamics and lost confidence: Greece’s crisis produced debt restructuring and an almost 30% economic contraction, while simultaneous declines in equities, bonds and currency can signal a credibility problem.
• The U.S. benefits from reserve-currency status and borrowing in its own currency, but net interest has surpassed defense spending as a share of GDP; after World War II, growth reduced debt-to-GDP from above 100% to below 30% by the mid-1970s, while the technology boom later lowered the ratio by about 10 percentage points.

Takeaway: Investors should not let debt headlines dictate major allocation changes, but should prepare for structurally higher debt, greater fixed-income volatility and tighter policy constraints; inflation would favor risk-managed and liquid-alternative strategies, whereas weaker growth would support high-quality and long-duration government bonds.