As Washington wrestles with the roughly $600 billion “fiscal cliff” and the 2013 budget, the far greater fiscal challenge of the U.S. government’s unfunded pension and health-care liabilities remains offstage. The truly important figures would appear on the federal balance sheet—if the government prepared an accurate one. …

The actual liabilities of the federal government—including Social Security, Medicare, and federal employees’ future retirement benefits—already exceed $86.8 trillion, or 550% of GDP. For the year ending Dec. 31, 2011, the annual accrued expense of Medicare and Social Security was $7 trillion. Nothing like that figure is used in calculating the deficit. In reality, the reported budget deficit is less than one-fifth of the more accurate figure.

Why haven’t Americans heard about the titanic $86.8 trillion liability from these programs? One reason: The actual figures do not appear in black and white on any balance sheet. But it is possible to discover them. …

Were American policy makers to have the benefit of transparent financial statements prepared the way public companies must report their pension liabilities, they would see clearly the magnitude of the future borrowing that these liabilities imply. Borrowing on this scale could eclipse the capacity of global capital markets—and bankrupt not only the programs themselves but the entire federal government.