Yeah. And the fix for that has nothing to do with “de-duping” as a database operation either.

The main components would probably be:

1. Decide on a new scheme (with more digits)
2. Create a mapping from the old scheme to the new scheme. (that’s where existing duplicates would get removed)
3. Let people use both during some transition period, after which the old one isn’t valid any more.
4. Decide when you’re going to stop issuing old SSNs and only issue new ones to people born after some date.

There’s a lot of complication in each of those steps but none of them are particularly dependant on “de-duped” databases.