NEW YORK (CNN/Money) - Consumer spending is the backbone of the U.S. economy, and consumers often bear the burden like a nation of pack mules.

In fact, U.S. consumers were toting around a much bigger debt load in September than they were in August, according to the latest government data. Still, the debt load may not be as weighty as it first appears.

According to the Federal Reserve, consumer credit rose at annualized rate of 9.7 percent in September, up from 5.5 percent in August.

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The big jump was due mostly to a sharp increase in nonrevolving credit -- which includes loans taken out for cars, education, mobile homes and vacations. Nonrevolving credit grew at a rate of 12.5 percent, well above the 7.1 percent rate booked in August. In dollar terms, consumer debt on non-revolving loans rose $12.1 billion in September versus a $7.1 billion increase in August.

The majority of that increased debt load is likely to have come from auto loans, since many consumers were buying cars in August thanks to strong incentives, such as zero percent financing deals or cash-back deals, said Mark Zandi, chief economist of Economy.com.

With regard to revolving credit -- which are loan accounts that do not require that you pay your monthly bill in full, the biggest example of which is credit cards -- the growth rate increased to 5 percent from 2.9 percent in the prior month. In dollar terms, consumers took on about $3 billion more in revolving debt than they had in August.

That may be because consumers, who had an infusion of cash from tax cuts and refinanced mortgages at the beginning of summer, may have run out of that cash but didn't necessarily want to stop spending, Zandi said.

But it may also reflect increased use of credit cards for convenience, he said.

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The Fed data provide a snapshot of credit card balances owed at a given time, but the numbers don't distinguish between those consumers who carry a balance on their credit card -- presumably because they can't afford to pay off the whole amount -- and those consumers who pay off their balances every month.

And in fact, according to research from Moody's Investment Services, consumers' repayment rate of credit card balances has been improving.

That doesn't mean, of course, that most Americans live debt-free. The average American carried $8,940 worth or revolving debt as of the end of last year, according to Cardweb.com.

The Fed's report on consumer credit does not include mortgage and home equity loans. Those, combined with consumer credit, are still at relatively high levels. According to Economy.com, nationwide household liabilities have grown 24 percent since the start of the past recession, which is 10 percentage points more than they were during the last recession in 1991.

To find out how your debt levels in different areas compare with that of other Americans, click here. And to find out if you're spending too much on your car, click here.