Privacy advocates are warning consumers to be selective in how they answer retailers' requests for their zip codes.
Paul Stephens, director for Privacy Rights Clearinghouse, said retailers use credit card customers' zip codes to connect their names and card numbers to their addresses and demographic data.
"That may let them do some telemarketing or send you catalogs," said Randy Hutchinson of the Better Business Bureau.
"Obviously, if I go into a store and make a purchase, I don't expect -- unless I sign up for a mailing list -- that I'm going to start receiving catalogs from the store," Stephens said.
Grocery stores include customers' zip codes among the data in their customer loyalty card programs.
"The information that Kroger has received voluntarily from our customers enables Kroger to mail special offers, based on their purchases in their local Kroger store," said Joe Bell, spokesperson for Kroger's Delta Division. "We do not sell, trade or rent our customers' personal information to outside companies or marketing firms."
Other zip code requests -- like the one when you swipe a credit card at a gas pump -- are security measures to protect the consumer's card.
"To verify that you are the owner of that card," said Hutchinson, "but then also retailers may want that information to decide where to put stores, what kind of merchandise to offer and maybe to send you some offers."
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