@Olivier5,
Veddy interesting. Will look at your link in a bit.
This brings up a personal story -
I've a long time woman friend who was born in Estonia (dark on the map, and her family members were scientists) and was in a DP camp in Sweden as a child before landing for good in Los Angeles. I was a bridesmaid in her wedding; the wedding was in a church. At that time, I was still a catholic but less so as the days rolled by, would blanket stop a year or two later.
Again the word fifty comes up - that was 1963.
My point - she and I, still close friends, have never talked about religion. Politics, art, men, children, dogs, cats, gardens, travel, food. Zip on religion. I'd not even noticed that before seeing that map.
Clue or not - she decorates like mad for Christmas, but does that mean anything? She's very craft oriented and a good painter and is keen to make holidays for children. (I probably won't ask now either)