Debt ceiling: Understanding what's at stake

(MoneyWatch) It is the economic calamity that no one expects and everyone fears.

Experts agree that failing to raise the nation's debt ceiling by Oct. 17, when U.S. officials say the government will run out of money to pay its bills, would gravely wound the economy, and perhaps even throw it back into recession. Because Treasury bonds and the dollar are cornerstones of the global financial system, meanwhile, the shock wave would be felt around the world.

"The potential is disastrous," said Gus Faucher, senior economist with PNC Financial Services Group. "We would see interest rates spike across the board. We'd see a huge crash in the dollar. People count on lending their money to the federal government and getting it back, and if that trust is taken away -- it's never happened that we haven't met our obligations as a nation -- then that has very, very negative consequences for the U.S. economy."

The consequences are so severe that, even as the government shutdown enters its second week, most seasoned political observers still expect Congress to ultimately reach an eleventh-hour deal to lift the government's borrowing limit.

But what exactly is the debt ceiling, and exactly how worried should Americans be that it could come crashing down?

What is the debt ceiling?

The debt ceiling is the total amount of money the U.S. government can borrow (by selling Treasury bonds) to pay its obligations, including interest on the national debt, Social Security and Medicare benefits, and many other payments. That limit is currently $16.7 trillion, although technically the government already exceeded it in May. The Treasury Department has since used various measures to continue borrowing.

During World War I, amid uncertainty regarding the total costs of funding U.S. involvement in the conflict, Congress created the cap in 1917 to put an upper limit on federal borrowing. Since 1960, Congress has raised the debt ceiling 78 times.

How is the debt ceiling changed?

Lawmakers can adjust it by passing a standalone bill or by including it in another piece of legislation as an amendment.

Does raising the debt ceiling increase the federal debt?

No. Lifting the borrowing limit simply allows the government to pay its existing bills. That debt exists whether or not Congress authorizes additional borrowing, and to avoid default it must be paid.

Why can't Congress and the White House avoid lifting the cap by cutting federal spending?

Because preventing the government from borrowing to meet its obligations would require all discretionary spending, such as for defense, education, housing and other annual appropriations, to stop, according to the Congressional Research Service. Most of the outlays for mandatory programs, such as Social Security, also would have to be halted, while taxes would need to rise to ensure the government had money to spend. Deep spending cuts and tax hikes would throw the economy into recession.

Why is Oct. 17 a critical date?

Treasury Secretary Jacob Lew recently forecast that on Oct. 17 the government would have about $30 billion on hand. That isn't enough because the government spends as much as $60 billion per day. "If we have insufficient cash on hand, it would be impossible for the United States of America to meet all of its obligations for the first time in our history," he said last week in a letter to congressional leaders.

What happens if Congress doesn't raise the debt ceiling?

If the government runs low on cash, it will have to withhold a range of payments. Retirees might not get their Social Security checks, especially worrisome for the millions of Americans who depend almost entirely on the social insurance program for income. The same goes for Medicare and Medicaid recipients. Holders of Treasury notes, from Wall Street and other global banks to foreign governments, also could get stiffed, jeopardizing the solvency of many financial institutions and choking off global credit flows.

The U.S. also would struggle to pay the interest on its debt, including a $6 billion payout due at the end of the month. At that point, the U.S. would be in default of its obligations. The value of Treasury bonds and the dollar would nosedive. The nation's borrowing costs would soar as anxious investors demanded a higher return to buy suddenly shaky U.S. debt. And because the interest rate on Treasuries provides a benchmark for rates on other loans, from mortgages and credit cards to car and student loans, borrowing would become far more costly for consumers and businesses. Stock markets in the U.S. and elsewhere around the world would almost certainly plunge.

"When stock prices fall, investment or other spending to expand a business is more costly," the Treasury Department said in a report last week outlining the potential impact of the debt-ceiling fight. "The effects on households and businesses, moreover, are reinforcing. Less capacity and willingness of households to spend, when businesses have less incentive to invest, hire and expand production, all lead to weaker economic activity."

In short, the already fragile economic recovery could stall.

Haven't we been here before?

There is recent precedent for such turmoil. Consumer confidence plummeted after lawmakers squared off over the debt ceiling in the summer of 2011, while the Standard & Poor's 500 stock index dropped nearly 20 percent. Hiring among small businesses slowed. Ever after a deal was struck to raise the cap in August of that year, credit rating agency Standard & Poor's downgraded U.S. debt for the first time ever.

Beyond the immediate economic fallout of defaulting on its debt, for the U.S. the symbolic blow might be even greater. In the post-World War II era, Treasuries and the greenback have -- for better and for worse -- served as the foundation of the global financial system. A default would shatter the faith on which that system relies.

How much danger are we in?

Although financial markets are not yet in panic mode, the standoff in Washington has them worried. Unlike during the 2011 dispute, when Republicans and most Democrats favored cutting federal spending, the stark division over Obamacare suggests there may be less room for compromise this time around. One clear sign of distress: Interest rates on short-term Treasury bonds rose last week, as investors seek greater yields to offset what they perceive as the greater risk of holding the debt.

Still, most economists, stock analysts and, for all the pointed rhetoric on Capitol Hill, even congressional leaders themselves downplay the chances of a default. The belief is that common sense, or at least a sense of political self-preservation, will prevail.