This could be ruled out as the explanation by looking at deceased records as well - if people who died around the age of 30 in the 1950s, 40 in the 1960s etc. a

This could be ruled out as the explanation by looking at deceased records as well - if people who died around the age of 30 in the 1950s, 40 in the 1960s etc. also all had curiously “round” birthdays then we could chalk up the fraud to poor recordkeeping instead. I’d be kind of surprised if such a coincidence hadn’t been previously noted though, surrounding discussion of the “birthday paradox” for instance.