Basically, if you don't know what this is, this is the demographic transition model. Every country goes through this and most have, but some haven't yet. Stage 1 - High death, high birth. Equal balance but low population. Stage 2 - Same birth, but lowering death, therefore rising population. Stage 3. Birth lowers, death lowers, and population grows. Stage 4. All 3 stable out again, but instead of high birth, high death, low population, we have low birth, low death, high population. Same balance but swapped.
