The Transition Every Society Has Run
For most of human history, births and deaths were both high and population stayed flat. Then society by society, a predictable four-stage Demographic Transition unfolded in a strict order:
| Stage | Births | Deaths | Population |
|---|---|---|---|
| 1. Pre-transition | High | High | Flat, brutal fluctuations |
| 2. Mortality drop | High | Falling | Explodes |
| 3. Fertility drop | Falling | Low | Growth decelerates |
| 4. Post-transition | Low | Low | Flat at a higher level |
The lag is everything. Deaths fall first due to sanitation and food, while births keep going because social habits adjust slowly. That gap between the curves is the population explosion. Every population boom is simply Stage 2, and every Stage 2 eventually ends as fertility drops worldwide.
Why Births Fall & Migration Realities
Fertility decline is driven by the shifting value of a child: child mortality falls, schooling replaces child labor, urban living makes kids expensive, and women gain education and options.
Migration is governed by two crucial overlooked factors:
- Networks: People migrate to where someone they know is, creating lumpy, chain-migration flows to known places rather than optimal ones.
- The middle move: The poorest rarely migrate because leaving is costly. Development initially increases emigration by giving people the funds to move.
Most migration is short-range, circular, and repeated rather than massive one-way permanent resettlement.