Opinion of these charts ...

[Linus Van Pelt]

I believe this is concentrated among hippy types and among Amish/Mennonites.

There is also considerable variation in state licensing of midwives for home birth. Ohio was a potential counterexample to my Amish theory, but a quick Google search suggests that the state has essentially no midwife licensing and is perceived as very home-birth unfriendly. So the rate outside Holmes county and surroundings is likely very low.