What does a number give away?
Run it backwards: where it was issued, and when its holder was probably born.
Read a number backwards
The first three digits of a social security number indicate the state that issued it, and the two after them place it in that state’s issuance order. Comparing this to nearby records lets us estimate when the person with a given number was born.
How the date is worked out
Numbers were handed out in a fixed order within each state: serials count up from 0001, then the group advances, and the area numbers cycle before it. That order tracks time, so a number’s place in the sequence is close to a date.
The lookup finds the forty records nearest this number in that sequence and reports when those people were born — the middle date, and the range the middle half of them fall in. Serials count up inside a prefix, so the last four digits move the estimate within it: in Alaska, 574-21-0001 and 574-21-9999 lie almost a year apart.
The records on this site only cover births from 1988 to mid-2011. Earlier in the sequence than anything here means a holder born before 1988. Later means the number was assigned at random, after the SSA stopped issuing them sequentially in June 2011. The same goes for the ranges never issued in state order at all, which is most of 700 upward.
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