@brianfenton My understanding is that it's possible to get a new SSN in the US, in which case there is definitely not a one-to-one mapping between SSNs and persons.If you mean SSNs more generally as in "mostly-numeric personal identification number generally assigned by a government entity" and are willing to consider international usage, then it's *very* possible for multiple people to have the same string of characters as their identification number.@thisismissem @phette23