U.S. federal debt could reach 210% of GDP within 14 to 20 years, according to projections by Kent Smetters, faculty director of the Penn Wharton Budget Model. Smetters and his team estimate that the U.S. federal debt cannot exceed approximately 210% of GDP. He asserted that beyond this threshold, no broad-based tax on labor income could generate enough revenue to cover the interest payments demanded by investors.

The Penn Wharton Budget Model projects a one-in-four chance for the U.S. to reach a 210% debt-to-GDP ratio in 14 years. Under historical assumptions of excess health care cost growth, the model anticipates this ratio will be reached within 20 years. The median scenario places the closure year at 2045 if health care costs increase rapidly, or 2051 under more optimistic assumptions.

Smetters cautioned that financial markets operate on the belief that Congress will eventually address fiscal issues, but this belief could change. "The assumption is that the financial markets are being set in a way where they keep believing that Congress will eventually get its act together up until the point where it's mathematically impossible for that to be true anymore," Smetters said. He added that the unraveling of financial markets could occur at any time investors lose confidence in Congress's ability to act.

The Penn Wharton Budget Model's April estimates show that retirees aged 65 and older receive $2.7 trillion, which represents 38.6% of total federal outlays and 61.9% of age-assignable spending. In contrast, working-age adults aged 26 to 64 receive $1.2 trillion, accounting for 27.9% of age-assignable spending. Children and young adults under 26 receive $449 billion, or 10.3% of age-assignable spending. "We do spend about 10x more per older person than we do per younger person," Smetters said. "In total, we spend about 6x in aggregate on older people than younger people."

Smetters noted that the Social Security main old-age fund has a confirmed depletion date around 2032, as reported by the Social Security Trustees and the Congressional Budget Office. After this fund is exhausted, the program could pay only about 83% of scheduled benefits, a fraction that Smetters estimated would further erode over time. "The last time we fixed Social Security in 1983, we waited very close for bad things to happen," he said. "The question is, how long can they get away with that?"

No independent assessment of Kent Smetters’s claims was available.