Each year, banks reap billions of dollars from overdraft and other fees. A new analysis of more than 500,000 U.S. users on Stash, a banking and investing app, found women pay a disproportionate amount of those penalties.

Male Stash users, the survey found, pay US$182 per year in fees, while women pay US$214, or 18 per cent more. That includes late fees as well as charges for ATMs, minimum balances, commissions and more, but overdraft charges make up the lion’s share. Women pay almost 30 per cent more in overdraft fees compared with men, the survey found.

“The main reason we think this is happening is the pay gap,” said Stash CEO and co-founder Brandon Krieg. Women earn about 20 per cent less than men on average, he said, and therefore have less money in their bank accounts, making them more likely to overdraw and incur penalties.

A decade ago, the federal government passed the Overdraft Protection Law to protect consumers from excessive banking fees, and for a while, overdraft fee revenue dropped. It’s since bounced back, according to a 2018 survey from Moebs Services.

In 2017, Americans paid US$34.3 billion in overdraft fees, a high since the regulation went into effect. That’s partly because the average fee went up from US$20 per transaction in 2000 to US$30, the researchers found. Last year, the four largest banks collected US$5.1 billion in overdraft fees alone, a number that has held relatively steady over the last three years.

This year, the Consumer Financial Protection Bureau opened a review of the rule. Banks and consumer advocates alike have urged the agency to keep it as is.