Payday lenders thrive on cash-strapped regulars.

That's according to the California Department of Business Oversight, which oversees the state's booming payday lending industry.

The number of customers who obtained 10 payday loans in 2015 outnumbered those who obtained just one, the state agency said in a report Wednesday.

More than 462,000 customers took out 10 payday loans last year, or 42% more than those who took out a single loan, according to the report.

The results highlight a long-held concern among consumer groups and regulators: that short-term loans often leave borrowers trapped in an expensive — and, at times, inescapable — cycle of debt and related fees.

"The numbers in this report reflect repeat customers' significant role in the payday loan sector," Jan Lynn Owen, commissioner of the department, said in a press release. "The data also raise questions related to the debt trap issue that is central to the debate over proposals to more strictly regulate the industry."

The findings come just weeks after the Consumer Financial Protection Bureau released its payday lending plan. The proposal, among other provisions, requires lenders to determine whether customers can repay their loans without reborrowing.

The California regulator's report shows that repeat customers are big business for the payday lending industry.

Subsequent transactions from the same borrower accounted for 83% of the total value of payday loans last year, based on a state survey. Nearly half of those loans were made on the same day that the customers' previous loan ended.

The average size of the two-week loans in 2015 was about $240, with an average annual percentage rate of 366%, according to the report.

The maximum transaction amount under state law is $300.

Overall, California payday lenders made $4.2 billion in aggregate loans in 2015, a 23% increase from a year earlier.

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