The U.S. economy may be strengthening, but by one measure Americans are flunking the basics of personal finance.

Credit card debt is ballooning, leaving American households with a net increase of $57.1 billion in new credit card debt in 2014, according to a new survey from CardHub. The credit card comparison site said it's forecasting new credit card debt will rise 5 percent in 2015, reaching $60 billion this year.

While the increased spending could signal that Americans are feeling more sanguine about their prospects and the economy, it's also a cause for concern given that most workers aren't seeing the type of wage growth that would support that higher spending. The surge has left the average household credit card balance at almost $7,200, or not far from the $8,300 level that CardHub considers unsustainable.

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"We've now had six consecutive quarters of year over year increases in our credit card debt load," CardHub said in the study. "As a result, we must strive to remember the corrosive impact of debt on household finances during the recession and work to get out from under its influence before the burden becomes unbearable again."

While Americans are carrying more debt, their earnings are barely ahead of where they were a decade ago. Household earnings have increased only 2 percent during the past 10 years, The Pew Charitable Trusts said in a study issued last month.

"That $8,300 figure was the average credit card balance back in the throes of 2008 when the economy started taking the downturn," said CardHub spokeswoman Jill Gonzalez. "This is a sign that Americans haven't really learned their lesson. Their attitude toward credit card debt hasn't improved since the recession."

On the other hand, Americans are feeling more positive about the economy, which is also reflected in their credit card debt, she added. The company expects 2015 to be a record year for auto sales, as Americans shop for new vehicles amid a brighter outlook, Gonzalez said.

More than half of Americans say they're financially insecure, citing concerns ranging from student loans and credit card debt to a lack of income, Pew found. With more than half saying they aren't prepared for a financial emergency, American's rising credit card debt could pose a problem if interest rates rise or the economy falters.

Still, some signs show that Americans are handling their debt levels, thanks to an improving job market. The credit card charge-off rate, or the percentage of debt that's declared unrecoverable by credit card companies, is about 2.89 percent, the lowest since 1985, CardHub said.

"While this speaks volumes about the strength of the economy, indicating that more people have jobs and are able to stay current on their financial obligations, the prodigious amount of debt that we continue to rack up indicates that consumer attitudes toward money have not improved since the Great Recession," the study noted.

Indeed, credit card debt has surged in the last two years, CardHub found. Last year's $57.1 billion in new card debt is a jump of 47 percent compared with 2013 and a 55 percent leap from 2012.