The increase in older women giving birth has not offset the birth rate decline.
Also there will be other side effects to deal with, there are statistically more developmental problems when women give birth later in life, possibly related to why autism is on the rise, it is more common among children born to older women.
If Autism increases starting when mothers are 30 years old... And the average age of a womans 1st birth is moving from 30 to 35 years old... And the only age group of women that had birth rate increase was 40+ years old. Interesting demographics...
https://drexel.edu/now/archive/2014/April/Autism-Risk-Older-Parents/