This might not be relevant in all country's, but I noticed that most young people today have less and kesz kids, or well most of them don't even want kids... Or if they have kids it's at a very late stage of their lives... Im sure this would also have an impact on the number of births.

I take myself for instance if I had kids the same age as my mums, those kids would be 5 to 7 years old now. Yet I'm not even married yet.