Though Social Security uses slightly different methods, the official numbers are expected to roughly track the Congressional projections, which were one page of a voluminous analysis of the federal budget proposed by President Obama in January.

Mr. Goss said Social Security’s annual report last year projected revenue would more than cover payouts until at least 2016 because economists expected a quicker, stronger recovery from the crisis. Officials foresaw an average unemployment rate of 8.2 percent in 2009 and 8.8 percent this year, though unemployment is hovering at nearly 10 percent.

The trustees did foresee, in late 2008, that the recession would be severe enough to deplete Social Security’s funds more quickly than previously projected. They moved the year of reckoning forward, to 2037 from 2041. Mr. Goss declined to reveal the contents of the forthcoming annual report, but said people should not expect the date to lurch forward again.

The long-term costs of Social Security present further problems for politicians, who are already struggling over how to reduce the nation’s debt. The national predicament echoes that of many European governments, which are facing market pressure to re-examine their commitments to generous pensions over extended retirements.

The United States’ soaring debt — propelled by tax cuts, wars and large expenditures to help banks and the housing market — has become a hot issue as Democrats gauge their vulnerability in the coming elections. President Obama has appointed a bipartisan commission to examine the debt problem, including Social Security, and make recommendations on how to trim the nation’s debt by Dec. 1, a few weeks after the midterm Congressional elections.

Although Social Security is often said to have a “trust fund,” the term really serves as an accounting device, to track the pay-as-you-go program’s revenue and outlays over time. Its so-called balance is, in fact, a history of its vast cash flows: the sum of all of its revenue in the past, minus all of its outlays. The balance is currently about $2.5 trillion because after the early 1980s the program had surplus revenue, year after year.

Now that accumulated revenue will slowly start to shrink, as outlays start to exceed revenue. By law, Social Security cannot pay out more than its balance in any given year.