U.S. banks, struggling with slow revenue growth, increasingly are setting their sights on customers who have only basic bank accounts, according to a new survey by KPMG LLP.

About 23% of bankers polled say so-called underbanked customers present the greatest growth opportunity for their bank, according to the KPMG study. That is up from 12% a year ago and represents the biggest jump among any category of customers.

KPMG defines underbanked customers as those who have a basic checking account but no access to other services, like credit.

Roughly 10 million, or 8.2%, of U.S. households are unbanked, according to data from the Federal Deposit Insurance Corp. Separately, 24 million, or 20.1% of U.S. households, are underbanked.

KPMG notes that the underbanked segment goes beyond low-income customers to include high-school and college students or recent graduates.

Banks increasingly are interested in underbanked customers because they spend more money on fees on things like cashing checks or ATMs than other customer segments, said KPMG, citing a study by Tufts University.

The KPMG survey polled 100 executives at banks of various sizes during the second quarter.

“Banks are getting more creative and thoughtful about how they target unbanked and underbanked customers,” said Judd Caplain, KPMG’s Advisory Industry Leader for Banking and Diversified Financials.

He added that banks are attempting to customize product offerings for this segment, and are staffing their branches to cater to them.

Separately, the KPMG survey shows that expanding the branch footprint continues to be a goal for many bankers, despite the rise of mobile banking. Roughly 41% of bankers polled said they plan to increase the number of physical branch locations over the next 12 to 19 months.

Brian Stephens, who heads KPMG’s banking and capital-markets business, said the figure goes hand-in-hand with a renewed focus on the unbanked or underbanked, who may be less likely to have access to smartphones or computers.

The survey also shows that 32% of bank executives believe that asset and wealth management, a less capital-intensive areas of banks’ businesses favored by some banking regulators, will be the top growth driver for their banks over the next one to three years.

Firms like Morgan Stanley, which has a large wealth-management business, have recently seen their stocks perform better than banks with big trading and markets businesses.