[eesmith]

I wonder if there how those low numbers have changed over time. I ask from personal history.

My grandfather was away in WWII when one of my aunts was conceived. As my grandmother put it, she was lonely.

All of the adults at that time knew, but kept it a secret. None of the kids knew until that aunt was about 45 and diagnosed with a cancer ... with a genetic susceptibility passed down though the male line. My grandparents figured it was time to reveal that secret.

I therefore conjecture that the numbers in the US were higher during WWII.