Except for some insular subcultures (such as the Amish, to give only one example among many). These subcultures are continuing exponential growth unabated, and

Except for some insular subcultures (such as the Amish, to give only one example among many). These subcultures are continuing exponential growth unabated, and eventually this will affect national and world fertility rate statistics. But such subcultures are still less than 1% of the population in the developed world, so even doubling their numbers every 20 to 25 years, it will take a while for them to have a statistically significant impact.