Why Cities Grow: People on the Move and the Demographic Transition
🎒 with Atlas
Atlas the geographer stands before a glowing wall map, tracing arrows of migration from countryside to a brightly lit growing city skyline, alongside a chart showing birth and death rate curves rising and falling across four labeled stages.
Explain how birth rates and death rates change across the four stages of the demographic transition model.
Distinguish between push factors and pull factors that drive human migration.
Analyze how migration and natural increase combine to produce urbanization.
Interpret population distribution to identify densely and sparsely settled regions.
Key terms
Population distribution
The pattern of where people live across a territory, from dense clusters to sparse areas.
Push factor
A negative condition such as war or drought that drives people away from a place.
Pull factor
A positive condition such as jobs or safety that attracts people toward a place.
Natural increase
The difference between births and deaths in a population, excluding migration.
Urbanization
The growing share of a population living in cities, driven by migration and natural increase.
Two Engines of Population Change
A region's population changes through two distinct engines: natural increase and net migration. Natural increase is births minus deaths within the population, so a place can grow even with no one moving in. Net migration is the balance of people arriving versus leaving, shaped by push factors that drive people out and pull factors that draw people in. The two engines often reinforce each other: during Stage 2 of the demographic transition, high natural increase coincides with heavy rural-to-urban migration, and together they produce the rapid urbanization seen in many industrializing nations.
Urbanization Versus Population Growth
Urbanization is frequently confused with overall population growth, but they are separate measures. Urbanization tracks the share of people living in cities, which can rise even if a country's total population is flat, simply because people relocate from countryside to city. Conversely, a mostly rural country can experience large national population growth without much urbanization. Cities then exert their own gravitational pull, building transit, housing, and economies that attract still more migrants. Keeping the two concepts distinct is essential for interpreting demographic data accurately.
Worked examples
Identify the rapid-growth demographic stage
Recall the stage definitions: Stage 2 features falling death rates with still-high birth rates.
Compute the effect: the gap between high births and dropping deaths yields the largest natural increase.
Match to the question: the stage producing the fastest growth is Stage 2.
Answer: Stage 2, because death rates fall sharply while birth rates remain high.
Predict the effect of Stage 2 growth plus rural-to-urban migration
Identify the first engine: in Stage 2, births far exceed deaths, so natural increase swells the population.
Add the second engine: large numbers of rural workers move to cities for factory jobs.
Combine them: natural increase plus in-migration both add to city size, producing especially fast urbanization.
Answer: Rapid urbanization, because natural increase and rural-to-urban migration both inflate city population.
Hello, I'm Atlas, and today we follow people across the map. Population distribution describes where people live; humans cluster near fertile land, fresh water, mild climates, and jobs, leaving deserts and high mountains sparse.
Over time, regions move through the demographic transition. In Stage 1 both birth rates and death rates are high, so population grows slowly. In Stage 2 death rates fall first — because of better food, sanitation, and medicine — while birth rates stay high, so population grows fast. In Stage 3 birth rates begin to fall as families choose to have fewer children, more women enter education and work, and economic conditions shift, among other reasons. In Stage 4 both rates are low and population growth levels off.
Migration is the other engine of population change. Push factors drive people away from a place: war, drought, few jobs, or persecution. Pull factors attract people toward a place: jobs, safety, schools, family. Natural increase is the difference between birth rates and death rates — when birth rates are much higher than death rates, a region's population grows even before anyone moves. When natural increase (especially in Stage 2) combines with large-scale rural-to-urban migration, cities grow with remarkable speed — this is called urbanization. Cities then reshape the region with new transit, housing, and economies. If a term feels fuzzy, look back at the stage descriptions and try the sorting activity to lock it in.
Activity
Sort each reason a person moves into either a push factor or a pull factor.
Practice
Sort 'ongoing armed conflict makes a town unsafe' into a push factor or a pull factor and justify it.
Explain why a country's urbanization rate can rise even when its total population stays constant.
Common mistakes to avoid
Urbanization means total population is risingUrbanization specifically means the growing share of people living in cities, which can increase even when the national population stays flat.
Stage 2 growth is caused by rising birth ratesBirth rates stay high while death rates fall in Stage 2, and the widening gap between them, not a rise in births, drives the rapid growth.
Check your understanding
In which stage of the demographic transition does the death rate fall sharply while the birth rate stays high, causing rapid population growth?
A country is in Stage 2 of the demographic transition, so its birth rate is much higher than its death rate. At the same time, large numbers of rural workers are moving to cities for factory jobs. What is the most likely result?
A student says urbanization means 'the total number of people in a country is increasing.' Why is this incorrect?
Why do populations tend to be sparse in deserts and high mountain regions?
Recap
Population change runs on two engines: natural increase, the gap between births and deaths, and migration, shaped by push and pull factors. When high Stage 2 natural increase combines with rural-to-urban migration, cities swell rapidly through urbanization, which measures the share of people in cities rather than total population, so the two concepts must be kept distinct.
Reflect
What push or pull factors have shaped where your own family has chosen to live over time?
Social Studies