I’d assume this is just in America. Worldwide, both Islam and Christianity are growing exponentially. This is in countries with birth rates above replacement level, and religious people have more children. Just look at the ultra-orthodox in Israel.
The statement is made by a curial official so it means world wide. I’d say most of those who leave are young mena dn wmoen who haven’t taken final vows. That’s what discernment and a noviate period are all about.