Africa is ground-zero only because the Christians are abusing the opportunity to increase their numbers by relying on those in desperate need. This for that. Sure it still counts towards their percentage, but to me it's practically cheating and totally playing dirty.
I have yet to hear any account on the increase of Christians in US, Europe and elsewhere, you have any stats on hand? What I did hear about is the increase of younger practicing Christians, though as you have stated, I believe I recall them being evangelical.
shadha-
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You may shoot me with your words,
You may cut me with your eyes,
You may kill me with your hatefulness,
But still, like air, I'll rise.
BREAST CANCER