TRUE BELIEVERS? Easy, about the 8 and something millions of publishers. People that are able to put a face and go door to door, at least before the pandemia. However there are a lot of others that are "symphatizers" like one person that I know, he is not at meetings, etc. but one time say to me "In my heart, I know is the truth" !
So total worldwide? About 30 million, if not more. When the next GB 3.0 take charge that people easy are gonna be in the Borg, of course is gonna be different than now.