He was part of a panel this weekend at the MIT Museum. It was interesting to hear how widespread this problem of poor record keeping is for births and deaths. Up until quite recently (like the 1960’s for the US), many places were, and some still are, terrible about it. That didn’t even include things like China’s former one child policy.
It’s not just a curiosity that some people don’t actually know how old they really are. It has real effects. When you’re trying to make health care or retirement benefit decisions for a whole country, having bad population data is a serious concern. Life insurance actuaries probably treat out their hair over this sort of issue, too