Average credit card delinquency rates declined in all 50 states last quarter, the first such nationwide decline for a year, TransUnion LLC has reported.

The Chicago credit bureau warned in a report released Tuesday that recent improvements in delinquency trends are not necessarily evidence of an economic turnaround.

TransUnion analyzed the data of 27 million U.S. borrowers, who it said made up 10% of credit-using consumers.

The ratio of borrowers at least 90 days delinquent on bank card payments fell 15 basis points from the first quarter, to 1.17%, the bureau said. The second-quarter figure was 13 basis points higher than a year earlier.

The states with the highest 90-day credit card delinquency rates during the quarter were Nevada (2.19%), Florida (1.64%) and Arizona (1.52%). The lowest rates were in North Dakota (0.69%), Alaska (0.71%) and South Dakota (0.77%).

The average individual credit card debt was $5,719, down 0.99% from the first quarter but up 1.74% from the year earlier.

"The recent change in delinquency may be more the result of seasonal fluctuations rather than a marked turnaround in nonpayment credit card behavior," Ezra Becker, TransUnion's director of consulting and strategy, said in a press release. Credit card delinquency rates remain "well within" historical norms.

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