@matrix Every instance of that specific claim that I can find links a "soulcast.com" as a source, but the website doesn't exist anymore. And every time, it seems people just copied and pasted some piece of text.
So while there's probably some truth to the phenomenon, I wouldn't trust the 80% number.
Interesting read, that's for sure, but unless I missed something, I haven't saw the 80% statistic.
I found this:
https://www.sammyboy.com/threads/in-what-countries-is-incest-legal.125784/
Which includes your original quote. But I still would love to see where that statistic is taken from.