When Does US Federal Debt Reach an Unsustainable Level?
Penn Wharton Budget Model (PWBM)
Summary: PWBM estimates that—even under myopic expectations—financial markets cannot sustain more than the next 20 years of accumulated deficits projected under current U.S. fiscal policy. Forward-looking financial markets are, therefore, effectively betting that future fiscal policy will provide substantial corrective measures ahead of time. If financial markets started to believe otherwise, debt dynamics would "unravel" and become unsustainable much sooner.
Please consider When Does Federal Debt Reach Unsustainable Levels?
The U.S. "public debt outstanding" of $33.2 trillion often cited by media is largely misleading, as it includes $6.8 trillion that the federal government "owes itself" due to trust fund and other accounting. The economics profession has long focused on "debt held by the public", currently equal to about 98 percent of GDP at $26.3 trillion, for assessing its effects on the economy.
We estimate that the U.S. debt held by the public cannot exceed about 200 percent of GDP even under today's generally favorable market conditions. Larger ratios in countries like Japan, for example, are not relevant for the United States, because Japan has a much larger household saving rate, which more-than absorbs the larger government debt.
Under current policy, the United States has about 20 years for corrective action after which no amount of future tax increases or spending cuts could avoid the government defaulting on its debt whether explicitly or implicitly (i.e., debt monetization producing significant inflation). Unlike technical defaults where payments are merely delayed, this default would be much larger and would reverberate across the U.S. and world economies.
This time frame is the "best case" scenario for the United States, under markets conditions where participants believe that corrective fiscal actions will happen ahead of time. If, instead, they started to believe otherwise, debt dynamics would make the time window for corrective action even shorter.
The Debt Clock and other sites exaggerate the problem.