Why are the numbers 2, 3 and 4 worn out on a local gas station's ATM card keypad?

September 18, 2006 8:57 PM

Tonight I was paying at a gas station and I used the keypad to enter my pin. The numbers 2, 3 and 4 showed tremendous wear compared to all other keys except the enter key. It's the kind of stupid odd trivia that appeals to me. I Googled "common pin numbers" and it seems "123" is pretty common among the unimaginative. But that doesn't explain 2, 3 and 4 being so well-worn, and not 1. Can you?
posted by Bud Dickman to technology (25 comments total)

Some cards use 4 numbers, and then it'd be 1234. Maybe they replaced the 1? The 1 would also be common if people use a birth year (what did the 9 look like?)
posted by easternblot at 9:11 PM on September 18, 2006

Where do you live? Gas station card machines often make me enter my zip code (to verify a credit card). I would bet those pads are used as often to enter a zip as a pin. If you live somewhere where the zip is 223, or 224, that might explain it.
posted by crabintheocean at 9:16 PM on September 18, 2006

Just a guess, but I imagine lots of people use four (or three) letter words for their pins, and use the corresponding letters on the number keys. There aren't any letters on 1, and 2-4 cover the letters A-I, which I think would probably be used a lot.
posted by Espy Gillespie at 9:16 PM on September 18, 2006

I didn't even know that three digit PINs existed. I've only ever had four-digits, over the course of three or four bank accounts. Maybe that's why?
posted by croutonsupafreak at 9:43 PM on September 18, 2006

people withdrawing 20, 30 or 40 dollars maybe? (does this ATM let you take out multiples of 10?). 1234 as a pin number also would probably contribute.
posted by gauchodaspampas at 9:48 PM on September 18, 2006

Did the number keys serve any other function at this machine -- like for example, did the screen ever say "press 1 for Yes and 2 for No"? That might be another reason for their having more wear.
posted by LobsterMitten at 9:53 PM on September 18, 2006

Huh, that's interesting. That covers 3 of 4 numbers of the pin on one of my cards.
posted by tomble at 10:43 PM on September 18, 2006

Please mark me as best answer ;-)



People use words for their numbers as well as simple ones like 1234. On a phone, #1 has no associated letters. The addition of words to the simplest PIN numbers causes this wearing (I'm 99.9% sure).
posted by Kickstart70 at 11:09 PM on September 18, 2006

Except, Kickstart70, that someone already beat you to it. :)
posted by Civil_Disobedient at 1:15 AM on September 19, 2006

Quoting from cut-the-knot.org:

"With the view to the eerie but uniform distribution of digits of randomly selected numbers, it comes as a great surprise that, if the numbers under investigation are not entirely random but somehow socially or naturally related, the distribution of the first digit is not uniform. More accurately, digit D appears as the first digit with the frequency proportional to log10(1 + 1/D). In other words, one may expect 1 to be the first digit of a random number in about 30% of cases, 2 will come up in about 18% of cases, 3 in 12%, 4 in 9%, 5 in 8%, etc. This is known as Benford's Law. (I am grateful to Sara-Jayne Farmer for the idea to juxtapose Benford's Law with the result on distribution of digits discussed elsewhere. She also pointed me to a very fine article on Benford's Law in New Scientist (July 10, 1999, pp 26-30.)"
posted by iconjack at 1:22 AM on September 19, 2006

Benford's law is very interesting, but I'm not sure it would apply in this case. AIUI it's only valid for scale-independent statistics, and PIN numbers are either going to be random or often date-based.

It would also suggest that the '1' should be twice as worn as the 2, which disagrees with what we're looking at here.

The words idea sounds plausible, but I'd never considered using a word for my pin number. Do card terminals over there have letters printed on them, or are the letter/number combinations just well known enough already?
posted by OldMansHands at 3:26 AM on September 19, 2006

I've never associated a word with my own pin personally, but I know that at least one person has :)
posted by antifuse at 4:07 AM on September 19, 2006

True fact: I have a ten-digit PIN.
posted by Plutor at 5:03 AM on September 19, 2006

Could it be related to how people typically hold/ address the PIN inputting machine and how much pressure gets applied?
posted by yerfatma at 5:50 AM on September 19, 2006

antifuse: hilarious link.
posted by EastCoastBias at 6:02 AM on September 19, 2006

Maybe the number 1 is used so often that its key has been replaced, leaving the worn 2-4 keys behind?
posted by Sticherbeast at 6:45 AM on September 19, 2006

Thanks for all the answers.

The PIN pad had no other functions I could see, so "1 for yes" is unlikely.

I don't recall for certain, but I don't believe this pad had associated letters on the number keys.

And the covering of the pad was one plastic sheet, so replacing one button would not be possible.

So none of this explains the relative pristine state of the "1" key, which, given its popularity (I, for one, think it's a swell number), should be among the most worn.

Anyway. Fun to think about, if completely pointless.
posted by Bud Dickman at 7:17 AM on September 19, 2006

My guess is that there is a commercial service nearby that uses a common PIN number for multiple vehicles. Like a limousine service or trucking company.
posted by kokogiak at 7:32 AM on September 19, 2006

Am I the only one who doesn't have to do anything but slide the card to pay via credit card at a gas station?
posted by GregW at 7:48 AM on September 19, 2006

I don't believe this pad had associated letters on the number keys

Doesn't matter. People pick words, know the numbers for those words, and will use them in places where the letters aren't visible.
posted by Kickstart70 at 8:15 AM on September 19, 2006

Do card terminals over there have letters printed on them, or are the letter/number combinations just well known enough already?

yes. and unfortunately, it seems most european banks don't have them. this was an annoyance when I went overseas. (I use a word for my pin).

if I had to guess, I'd say that the combination of people with 1,2,3,4 PINs and people with word pins (seeing how three of five vowels and sometimes six are contained on the 2,3 and 4) keys could cause such wear.

why not just ask the dude at the store? Maybe he's noticed something (or they replaced the one key).
posted by fishfucker at 8:17 AM on September 19, 2006

GregW, I think they're talking about debit cards, not credit.
Personally, I don't need to enter anything for my credit card, but always do with my debit.
posted by utsutsu at 8:32 AM on September 19, 2006

I asked the dude at the store. "I dunno, bro," was his reply.
posted by Bud Dickman at 9:28 AM on September 19, 2006

And the covering of the pad was one plastic sheet, so replacing one button would not be possible.

Well, the covering obviously wasn't there from the beginning, or the keys wouldn't be worn, no?
posted by weapons-grade pandemonium at 9:54 AM on September 19, 2006

Can we get a picture of the keypad in question?
posted by Netzapper at 4:40 PM on September 19, 2006