Geography · Lesson g04

People on the Move: Population & Cities

Every year, millions of people pack a bag and start a new life somewhere else. Why do they go, where do they end up, and how can a graph tell the story?
A girl and her horse on a hillside looking down at a busy city of rooftops and a quiet green village, with small figures travelling toward the city

Your family moves around the world, so you already know that people travel for all kinds of reasons. In g01 you learned where people settle. Now we ask the next question: why do populations grow, why do cities swell, and why do people leave one place for another? Geographers answer with two tools you already own: a graph you can read, and percentages.

👥 Big idea 1: population and urbanisation

A place's population is the number of people living there. It grows when more people are born or arrive than die or leave. Urbanisation is the growing share of a country's people who live in towns and cities rather than the countryside. Today more than half of all people on Earth live in cities, and the share keeps rising.

Watch the difference: a number of people (how many) is not the same as a share of people (what percent).

🧳 Big idea 2: migration, push and pull

Migration means moving to live in a new place, usually for a year or more. A short holiday is a visit, not migration. Moving within one country (village to city) is internal migration; crossing a border is international migration.

Geographers sort the reasons into two kinds. Push factors drive people away from where they are (drought, no jobs, conflict, flooding). Pull factors attract them to somewhere new (jobs, schools, hospitals, safety, family already there). Most moves involve both.

Geography connection (g01): the "good place to settle" factors (water, flat land, trade routes) are exactly the pull factors that make cities grow. Big cities keep growing because they keep pulling.
Maths connection: percentages (like the interest in Lesson 23): to compare growth fairly, use percent change: $$\text{percent change} = \frac{\text{new} - \text{old}}{\text{old}} \times 100\%$$ The divide is always by the starting value. That is the one place people slip.
Population of Valleyton (invented figures) 01020304050 1990200020102020 Population (thousands of people) Year
Faint lines mark every 5 thousand people; numbers on the side are every 10 thousand. "30" means 30 thousand, which is 30 000 people. Valleyton is an invented town, made up for this lesson.
Worked Examples
Worked Example 1: percent change from a graph

Using the Valleyton graph, find the percent increase in population from 1990 to 2000.

Read: 1990 is 20 thousand; 2000 is 25 thousand. The change is $25 - 20 = 5$ thousand.

$$\frac{5}{20} \times 100\% = 25\%$$

The town grew by 25% in that decade. Notice we divided by 20, the old value.

Worked Example 2: push or pull?

A farming family leaves a mountain village for a coastal city. Two years of poor harvests left them short of money, and the village school has closed. In the city, a cousin has found them a place to live and the port is hiring.

Push factors (about the village they leave): poor harvests, the closed school. Pull factors (about the city they choose): port jobs, a cousin and a home waiting. Test: a push is a problem where you are; a pull is an attraction somewhere else.

Warm-Up
  1. Problem 1
    Look at the Valleyton graph. (a) Read off the population in 2010, as a full number of people. (b) Find the decade that added the most people, and state how many people it added.
    read the bar → compare the gaps between bars →
  2. Problem 2
    Decide whether each counts as migration (yes or no): (a) A family moves from a village in Oaxaca to Mérida to live there permanently. (b) A family spends two weeks of holiday in Mérida and then goes home.
    stay for good, or for a visit? →
Core Problems
  1. Problem 3
    Valleyton added 5 thousand people in the 1990s and also 5 thousand in the 2000s. Find the percent increase from 2000 to 2010, then say which decade grew faster in percent terms.
    percent change $= \dfrac{\text{change}}{\text{old}} \times 100\%$
    change ÷ starting value →
  2. Problem 4
    Between 2010 and 2020 Valleyton grew by 50%. Now imagine a big factory closes and, between 2020 and 2030, the population falls by 50%. Is Valleyton back to its 2010 population? Give the 2030 population and say how far it is from the 2010 figure.
    50% of which number? →
  3. Problem 5
    Country X is invented for this problem. In 1960 it had 10 million people and 30% lived in cities. In 2020 it had 40 million people and 60% lived in cities. (a) Find the number of city dwellers in 2020, in millions. (b) The percentage in cities doubled. By what factor did the number of city dwellers grow since 1960?
    percent of total → compare the two city numbers →
  4. Problem 6 Challenge
    Imagine Valleyton keeps growing from its 2020 population by 50% every decade. (a) Find its population in 2040. (b) How many more people is that than if the town had simply added the same 15 thousand people each decade after 2020?
    growth of a growth → compare with a steady add →
  5. Problem 7 Open
    Pick a family move you know about, from your own travels or an imagined one, from the countryside to a city or from one country to another. Name two push factors, two pull factors, and one difficulty the family might not expect when they arrive. There is no single right answer: make each factor belong to the right side.
    push (where from) · pull (where to) · surprise →
Think like a geographer 🧭: A graph shows how many people moved, but never why. Behind every bar is a person deciding between a place that pushes and a place that pulls. Good geographers read the numbers first, then ask what the people were feeling.
Show answers
Problem 1a
30 thousand = 30 000 people.
Problem 1b
2010 to 2020: it grew from 30 thousand to 45 thousand, adding 15 000 people (the others added 5 000 each).
Problem 2a
Yes. A permanent move to a new place is migration (internal, because it stays inside Mexico).
Problem 2b
No. A two-week holiday is a visit, not a move to live there.
Problem 3
5 ÷ 25 × 100% = 20%. The 1990s grew faster (25% against 20%), because the same 5 thousand is a bigger share of the smaller starting population.
Problem 4
2020 is 45 000. A 50% fall removes 22 500, leaving 22 500. No, it is not back to 30 000: it is 7 500 below the 2010 figure, because the 50% was taken from the bigger number.
Problem 5a
60% of 40 million = 24 million city dwellers.
Problem 5b
1960 city dwellers: 30% of 10 million = 3 million. 24 ÷ 3 = 8, so the number grew 8 times (the percentage only doubled).
Problem 6a
45 000 × 1.5 = 67 500 (2030); 67 500 × 1.5 = 101 250 in 2040.
Problem 6b
Steady adding gives 45 000 + 15 000 + 15 000 = 75 000. The difference is 101 250 - 75 000 = 26 250 more people.
Problem 7
Open. Check that push factors are problems at the place left (e.g. drought, no jobs, conflict), pull factors are attractions at the destination (e.g. jobs, school, safety, family), and the difficulty is realistic (e.g. high rents, a new language, missing home).
Next up → g05: Map Skills & Coordinates We have talked about where people live and move. To say exactly where, you need an address for every spot on Earth. Next we learn latitude and longitude, the coordinate grid wrapped around the planet, plus grid references, compass directions and map scale.
← All lessons
25:00

Ask your tutor