With new overdraft rules set to take effect Aug. 15, banks have been pleased to discover that most customers who overdraw their accounts, even occasionally, are giving them permission to cover debit-card overdrafts.

Those who don't spend what they don't have are generally declining overdraft protection.

But in between the opt-ins and the opt-outs is a large swath of consumers who haven't made up their minds. It's this group that is likely to get caught most off guard when the new rules kick in.

According to a survey the Nielsen Co. released in June, 39 percent of consumers were undecided about opting in for overdraft coverage. They were either still thinking about it or didn't really understand the new regulation.

In comparison, 26 percent said they would definitely opt in to overdraft programs and 22 percent said they would not.

For bankers trying to help the undecided make up their minds, it might help to know who they are.

Nielsen divided this group into four segments, including "working class" and "fiscal fledglings." The working class segment is ethnically mixed and nine of 10 earn less than $30,000 a year. The fledglings have the lowest levels of income and the fewest assets. While these undecided consumers might have the most need for overdraft protection, they are also least likely to be able to afford it.

Those who can afford the fees are more likely to sign up for overdraft protection. Nielsen found that many of the consumers readily opting in are "upscale earners" who either want cash available in case of emergencies or have multiple users on their cards and don't always know their balances. They also were likely to have had at least one overdraft in the past year.

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