Some stud may have to step up and keep the world growing.
But more on the fertility rate, the world is still growing but the family size is getting smaller and at some point there will be a decline, which will have to happen for mankind to survive in centuries to come.
I read about this some years back and some good projections are all out there if some want to look.
The link in here and the graph below is from within on the infographic link
