Seinfeld is still as strong as ever, 10 years after kicking the bucket. It’s spawned countless immortal pop culture lines, but as a marketing aficionado, one that’s always stuck with me is “Why does Radio Shack ask for your phone number when you buy batteries?”

A good question, albeit a very old one. (and let’s ignore the fact that Radio Shack barely exists anymore). It’s also oft-answered. I get this question a lot though in random conversations, so here it is.

As you complete a sale at RS, they’ll “ask” ..and what is your phone number starting with the area code? Out of reflex, people usually give the number, not thinking anything big of it because they’re seconds away from walking out of the store anyway.

It’s not like RS ever calls them, so it’s not a big deal when it happens again in the future.

The key part of your phone number is your area code. Having a record of how many people from a specific area code has purchased something in that store is valuable info. It allows them to see what people from the 543 region are buying, and what kind of numbers they are attracting versus other branches.

Maybe the branch covers 3 area codes, and only gets consistent sales from 2. This tells them that they should advertise in the delinquent area code, or mail out flyer specials to that area code. If they didn’t have that info, they might have advertised to all 3 area codes and thus needlessly overspending on advertising.

Although I’m noticing that cashiers rarely ask for your phone number these days, opting for your postal code — which does the same thing, and is way less intrusive.