It takes more than a few doubts about safety and soundness for banks to lose retail customers these days — or at least more than it used to.

Last fall, a bank ranking in the 70th percentile from a financial soundness perspective might have seen more than 20% of its customers reducing the balances in their primary accounts. By May, a bank in similar condition would have prompted only 5% to 10% of customers to trim balances, according to a survey by retail banking consulting firm Mercatus LLC.

But lest bankers start feeling comfortable again, a new front is opening up in the battle for wallet share.

Transparency on fees and quality of customer service figure greatly into customer perceptions of trust, and banks that fail to provide either will find it harder to recover the share of wallet that consumers entrust to their primary bank.

Anxious consumers have been reducing the share of deposits and other household assets entrusted to their primary banking institution, from an average of 44% in May 2008 to 36% in May 2009, according to Bob Hedges, managing partner at Boston-based Mercatus.

"Consumers' dispersion of deposits across several financial institutions is directly linked to levels of trust with a particular provider and their perceptions of financial soundness," Hedges said. "Consumers are particularly sensitive to the unanticipated charges and fees they experience, and this ultimately destroys trust in the banking institution."

Trust levels vary greatly by industry sector, according to the survey, which asked 1,050 consumers about their primary banks.

As of May, nearly 90% of consumers who kept checking accounts with community banks and credit unions said they trusted their primary bank, up from 84% a year earlier.

But trust scores dropped for large banks, from 79% to 75%; regional banks, from 72% to 71%; midsize banks, from 69% to 67%, and investment firms, which showed the most dramatic slide, from 72% to 56%.

But wallet share declined for banks in the past year regardless of where they ranked on the trust scale, the survey said.

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