People are always born with the same age namely 0, but they do not all die at the same age. In fact getting older increases chances of death. Hence 2 babies per mother ends up in a pyramid too.
Even if you presume people all die at the same age, things will be stable. If say people all get childten at 30 and only work between 30-60 and then all die at 90. If we then assume 1 child per couple and everybody has a child at 30, we would get a stable dependency ratio of 2.5 dependents per worker. Obviously those numbers are not realistic. Btw that also is not a pyramid, but a trapezoid.
People are always born with the same age namely 0, but they do not all die at the same age. In fact getting older increases chances of death. Hence 2 babies per mother ends up in a pyramid too.
Even if you presume people all die at the same age, things will be stable. If say people all get childten at 30 and only work between 30-60 and then all die at 90. If we then assume 1 child per couple and everybody has a child at 30, we would get a stable dependency ratio of 2.5 dependents per worker. Obviously those numbers are not realistic. Btw that also is not a pyramid, but a trapezoid.