When I was in school (almost 20 years ago) this came up because someone mentioned the first 6 digits of their SSN and they matched mine. Since then it's simila

When I was in school (almost 20 years ago) this came up because someone mentioned the first 6 digits of their SSN and they matched mine. Since then it's similarly bothered the hell out of me that the practice is to mask all but the last 4 of the SSN and that a lot of places require you to enter your last 4 of your SSN. I didn't know the reasons for the matches but them being my age and likely born in the same place as me made me realize those were identifiers and the last 4 were the unique bit.