"sometimes made themselves a year or two older. Presumably so that they could start collecting benefits sooner"

This is why the SSA used the actual birth record, and if that weren't available, the first census showing the person or some other record.

My mother, for example, had a birth record, but there was a fire in Buffalo City Hall at some point, and mother had to send the one she had for a Teacher's Certificate. So the SSA used the first census where she appeared. For immigrants, they might have used naturalization documents or passenger list information - the older the better for records, but they never took anyone's word for it.

Sally Bruckheimer
Princeton, NJ