Is a 4 digit SSN number suffix really enough to be helpful to them in that regard? I guess they could find all "jcater"s with those 4 digits and make assumptions, but that is far from unique.
ZipCode + SSN is enough to identify you, even without your name, close to 100% of the time. Toss in your name and I'd be amazed they'd ever got a false positive. I'm [honestly] not sure why they even bother asking for a mailing address other than to go from 99.9% confidence to 100%.
Fyi, there is ~8k people [on average] in a zip code. The odds of your name and SSN repeating inside a zip code is low. Name tho? Name could happen with reasonable odds. I used to know someone in my zip code with an identical first/last [not middle] name.
I'm going to give you the benefit of the doubt and assume you misread the post you are replying to, which referred to the last 4 digits of a SSN, and incorrectly assumed we were talking about full SSNs. Because otherwise your statement is absurdly wrong.
If there are 10,000 possible 4 digit combinations and 8,000 people in a ZIP code on average, the odds that someone else will share the last 4 digits of my SSN is 1-(1-1/10000)^7999 which comes out to 55%. So in reality, more often than not, you will share the last 4 digits of your SSN with someone in your zip code.
Also, there are a few zip codes with 100,000+ people in them, and many zip codes with 50,000+ people in them. These zip codes account for many millions of people. You are guaranteed that nearly every resident will share the last 4 digits of their social security number with at least one other person in these zip codes.
