Driven by higher interest costs, Social Security and Medicare for baby boomers, as well as tax cuts made permanent in 2012, the federal debt held by the public is expected to hit $40 trillion in 2035, according to calculations by the Committee for a Responsible Federal Budget based on Congressional Budget Office estimates. Back in 2009, soon after President Barack Obama took office, the forecast for the 2035 burden was at least $7 trillion lower.

In 2035, the debt will almost equal the size of the U.S. economy; four years later it will match the previous record, set in 1946, at 106 percent of gross domestic product, the CBO estimated last year. Compare that to the 2014 debt burden of $12.8 trillion, or 74 percent of GDP.

The economy just isn't growing fast enough to keep pace with the costs of caring for the soaring ranks of the elderly, and the discrepancy between spending and revenue is estimated to widen in the next few decades.