Population and Urbanization

Counting Humanity

Demography is sociology with the best data: births, deaths, and moves, each recorded and each remaking markets decades in advance.

The core rates (all per 1,000 people per year): the crude birth rate, the crude death rate, and their difference, the rate of natural increase. Add net migration and you have a country's whole population arithmetic.

$$\text{growth rate} = \frac{\text{births} - \text{deaths}}{1000} + \text{net migration rate}$$

A population growing at $g\%$ doubles in roughly $70/g$ years — the rule of 70 again, now applied to people.

The demographic transition is the master pattern of the last two centuries, in four stages:

1. Pre-industrial: high births, high deaths — population barely grows.
2. Early transition: deaths fall (sanitation, vaccines) while births stay high — the population explosion.
3. Late transition: births fall too (education, urban life, contraception) — growth slows.
4. Post-transition: both rates low; growth near zero, sometimes negative — the aging society.

Every country walks these stages; what differs is when and how fast. Europe took two centuries; parts of Asia compressed it into two generations.

Population pyramids photograph the transition: a wide-based triangle means stage 2 (young, exploding), a barrel means stage 4 (aging), an inverted base means shrinking cohorts — next decade's schools, workforces, and pension bills, visible today.

Urbanization is the transition's travel companion: since 2007, over half of humanity lives in cities, heading toward two-thirds. Cities concentrate labor markets, ideas, and consumption — Durkheim saw the shift from the village's mechanical solidarity (likeness) to the city's organic solidarity (interdependence of specialists).

For business, demography is destiny with a lag: baby booms become housing demand in 25 years and pension crises in 65 — the rare forecast a firm can actually bank on.

The demographic transition

Common pitfall: Expecting growth to stop when fertility falls. Demographic momentum keeps a young population growing for decades — the large cohorts already born still have their children ahead of them.