It's the quality that is changing, not the quantity. (though that has stopped growing in the developed world.)
In the developed world it is only the depressed and the mentally ill that are buying it. These and a few of the offspring of the depressed, mentally ill and deluded that are already in.
Healthcare and lifestyle in the "west" - with all its faults - has kept the 1975 generation (that remained in, like the present GB) alive in enough numbers to keep the show going until now.
The children of these are not as committed and the grandchildren are leaving or are only staying if they cannot cope with the disapproval and shunning of leaving.
It's hollowing out from the inside but the numbers will not largely change, I predict.