When you are born, there is a life expectancy assigned and I'm sure many factors are included, especially gender and race and how others that age fare. Mine was 65.2. Then the longer you live, the more that is adjusted. I received my withdrawal account for my TDAs and each year my balance/withdrawal is refigured based on my life expectancy. Now it is about 98. In other words, the money needs to last that long! That's sort of scary, isn't it?
My grandfathers lived into their 90s as did one of my grandmother's sisters (Ada) and my mother's sister (Muriel) and brother (Leslie). But not my parents. Looking back, none of those who lived into their 90s had any medical care as children--they weren't even born in a hospital.