There are more payday lenders in the U.S. than McDonald's or Starbucks, reflecting economic conditions in which fast money is even more important than fast food.

Payday lending, in which users pay a fee for what amounts to an advance on their paychecks, has blossomed over the past 20 years. There are now more than 20,000 across the country, according to the St. Louis Federal Reserve, while McDonald's boasts 14,267 locations.

They're used most often by people who lack access to ordinary credit—often those at or near the bottom of the economic spectrum, with nearly a quarter living on public assistance or retirement income.

While the loans can fill a need for fast cash, they also can become a way of life for users who end up paying effective annual percentage rates, or APRs, well in excess of 300 percent.

Consequently, they've attracted the attention of regulators, politicians and economists why worry about those left behind in a decidedly uneven economic recovery.

"A large number of Americans are literally living paycheck to paycheck. They're one unplanned expense away from being in financial distress."

"A large number of Americans are literally living paycheck to paycheck," said Greg McBride, chief financial analyst at Bankrate.com. "They're one unplanned expense away from being in financial distress."

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McBride cited some sobering statistics: Twenty-six percent of Americans have no emergency savings and 41 percent say their "top financial priority" is simply staying current with their expenses or getting caught up on their bills. This is occurring even as the financial headlines trump new stock market highs by the day and President Barack Obama's administration touts the U.S. economic recovery.

"Americans that have assets have seen the value of those assets appreciate, but Americans who don't have those assets, they're not feeling the recovery in their pocketbooks, particularly at a time of stagnant income," McBride said. "If you don't have those things, and you haven't seen a pay increase, then you're no better off, you're no wealthier."

Finding Themselves Poorer

Those using payday loans, in fact, may find themselves poorer.

The mean, or typical, payday borrower makes $22,476 a year and paid $458 in fees. However, a quarter of those borrowers paid $781 or more in fees due to repeat usage, according to the Consumer Finance Protection Bureau, which is closely monitoring the approximately $50 billion industry and will likely put forward more regulation.

About 48 percent of borrowers had done 10 transactions in the CFPB's time sample, and 14 percent had more than 20 transactions. The median borrowing amount was $350, for a 14-day term. Median fees for $15 per $100, which computes to an APR of 322 percent.

In all, consumers using payday loans were on the hook to their lenders for 199 days, or about 55 percent of the year.

"It appears these products may work for some consumers for whom an expense needs to be deferred for a short period of time. The key for the product to work as structured, however, is a sufficient cash flow which can be used to retire the debt within a short period of time," the CFPB wrote in a 2013 report studying the payday proliferation.

"However, these products may become harmful for consumers when they are used to make up for chronic cash flow shortages," the report continued. "We find that a sizable share of payday loan and deposit advance users conduct transactions on a long-term basis, suggesting that they are unable to fully repay the loan and pay other expenses without taking out a new loan shortly thereafter."

A year ago this month the bureau began accepting consumer complaints and received thousands soon after, according to the St. Louis Fed, which in its own recent report cited the potential for payday loans to "become a financial burden for many consumers."

Payday lending is allowed in 36 states, and fees are lowest in the states that regulate them.

Bankrate's McBride cautioned, however, that excessive regulation could be problematic if it ends up denying cash-strapped consumers who can't get conventional loans or credit cards access to emergency funds.

"That's a double-edged sword," he said. "In some ways it can benefit consumers but in some ways it can hurt consumers. Limitations on how often that borrowed amount can be rolled over could keep consumers from falling into a bottomless pit of debt. But there's certainly a fine line. These services exist because the demand is so high. The reality is a lot of Americans need short-term credit."