in reply to SSN's possible new Y2K problem?
If you think about it, until recently not everyone needed a SSN. At some point, not everyone needed an SSN: those not eligible (foreign workers depending on status prior to 1986, 1981, 1977, etc..), all of those stay-at-home parents who never worked or filed prior to 1988, any wage earner who chose not to participate prior to 1962, children prior to 1988 (and unclaimed dependants even now), and so on. So the SSA has only issued 140 million SSN's over the past 70 years. Don't get caught in the mental trap of using the SSN against population as an ID number, it doesn't quite work that way. It's not 1:1, and not even 1:N where N is constant over the last 70 years.
They've got plenty left for a while to go. Not another 70 years for sure, but for a while.