Rather than being about fast/simple/cheap, I think using SSN as a key was more about the fact that SSN is the only common identifier that almost all US citizens have.
replyI think you're using the word "key" differently than OP. You're talking about identifiers, and they're talking about security.
replySSNs were a good potential identifier, until the people that needed security cheaped out and started using SSNs as a bad implementation of security. Now they're bad at both purposes!
Yes, designing and implementing a new common identifier almost all US citizens have would have been less cheap and fast.
replyTax ids were never meant to be used as a form of global identification. If you go look in a real bank core, you'll find this field does not have any uniqueness constraints.
replyWhy not? Two people with the same tax ID seems like a problem waiting to happen.
replyThese schemas also support non-individuals with the same fields. EINs have a lot more edge cases than SSNs.
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