A new study shows midsize banks have the edge in making money from their retail customers.

Banks in the $10 billion to $35 billion category led the industry with $153 of profit per customer last year, according to Andersen Consulting. Those with less than $10 billion of assets earned only $108; "large" banks, with $35 billion to $80 billion of assets, made $134; and "super-large banks," with assets of more than $80 billion, made only $113 per customer, the firm said Thursday.

The result highlights the difficulty the biggest banks have faced keeping customers happy after megamergers, as well as the problem the smaller ones face making fixed costs pay off over a smaller customer base.

The midsize banks "are running pretty tight shops," said Rainer Famulla, the Andersen partner responsible for the survey. "They just do a lot with the customer base. They do develop personal relationships.

"It's clear that if you're very large, the scale isn't given to you automatically at all," he added. "It's something you really have to work for."

In addition to their fixed-cost problem, the smallest banks' relationships are less profitable because they tend to provide only one services to each customer, such as a checking or savings account, Mr. Famulla said.

Joseph A. Stieven, a bank analyst at Stifel, Nicolaus & Co. in St. Louis, said the results support his view that midsize banks have the greatest profit potential. "All these banks that acquired the No. 1, 2, and 3 market position will spend eternity defending those positions," Mr. Stieven said, noting earnings disappointments by some of the big buyers.

Mr. Stieven said it is better for a bank to enter a market in the No. 8 position and grow internally. "You'll be picking up market share from the big banks," he said.

He added that he believes the size cutoff for profitability is lower than the $10 billion in the Andersen study. "I see a lot of banks between $1 billion and $10 billion making a lot of money."

Andersen first conducted this survey last year, using data from the previous four years, Mr. Famulla said. The firm based its conclusions on publicly disclosed cost and revenue data, and surveyed companies to determine how each defines its customer relationships. Some count households, while others count individuals, he said.

This year's survey included data for other financial services firms and concluded that mortgage companies topped the field with $395 per customer in profit for the year, thanks in large part to the refinancing boom last year.

Self-service brokers made $114 per customer; full-service brokers made $179; mutual fund firms $80; and credit card firms, $30, the survey said. Such data will help would-be acquirers "to find or debunk" the potential for synergies in any proposed deal, Mr. Famulla said.

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