Anyone who doesn't think the Social Security Administration doesn't know, separately tracks and keeps its mouth shut about multiple uses of the same number is an abject idiot.
Detecting multiple use occurrences in a data base is one of the first tasks of managing one. For computers, yes even in the 80s this isn't/wasn't hard.
They do this because they want what grift they get from that taken from the illegal (who isn't off the books) and his employer for both SS and Medicare to start with. Mo Money.
They ALSO keep the multiple instances of the same number accounts separate, lest they have to credit the real owner with more income during his working career, and thus more payout.
Money grubbing bastards, and their duplicity is going to come home to roost when whatever quisling president (Bush?) legalizes them and they get their cred for what they've paid. Instant SS/Medicare insolvency.
This is a byproduct of our abortion policy. Since Roe, we have killed off some 30 million Americans - most of whom would likely now be “dues paying” American workers. We’ve replace our own slain workers with imported workers, whose main benefit to the USGovernment is to keep the SS pool afloat.