To interpret an urban-growth pattern, describe the change in numbers, compare the periods and then describe where on the map the change happens. It appears with maps, satellite-style images and tables in population and settlement evidence.
How do you interpret step by step?
- Name the measure and unit, for example built-up area in km².
- Find the change for each period, in absolute terms.
- Work out the percentage change if the question asks you to compare.
- Identify the fastest and slowest periods.
- Describe the shape on the map: direction, routes followed, edges.
- Add a limit: the data may not show why growth happened.
Worked example
Invented data for City E, built-up area.
| Year | Built-up area (km²) |
|---|---|
| 1990 | 40 |
| 2000 | 55 |
| 2010 | 90 |
| 2020 | 110 |
Absolute change: 1990 to 2000: 15 km². 2000 to 2010: 35 km². 2010 to 2020: 20 km².
Percentage change 2000 to 2010: 35 ÷ 55 = 0.6364, so 63.6%.
Per year, 2000 to 2010: 35 ÷ 10 = 3.5 km² per year.
Over the whole period: 110 − 40 = 70 km², and 70 ÷ 40 = 1.75, so 175% growth.
Description: “City E’s built-up area grew fastest between 2000 and 2010, by 35 km² or 63.6%. Growth then slowed to 20 km² in 2010 to 2020.” Suppose the map shows new buildings along the northern road. Then add: “New housing is stretched along the northern road, a ribbon pattern.”
The mistake to watch for
Mistaken answer: “The city grew steadily because the line always goes up.”
The line rises in every period, but the amounts differ: 15, 35 and 20 km². “Steadily” claims equal steps.
Correction: give the change for each period and say which is largest. Use “steadily” only if the changes are close to equal.
Self-check
1. Using City E, work out the percentage change from 1990 to 2000.
Show answer
15 ÷ 40 = 0.375, so 37.5%.2. And from 2010 to 2020?
Show answer
20 ÷ 90 = 0.2222, so 22.2%.3. In which period was the absolute change largest and in which was the percentage change largest?
Show answer
Both were largest in 2000 to 2010: 35 km² and 63.6%, compared with 15 km² and 37.5%, and 20 km² and 22.2%.Where does this lead next?
Growth figures are a kind of average over a whole city, so the next lesson asks what an average can hide. Continue with distinguishing an average from a distribution.
Earlier work on comparing settlement functions helps explain why growth takes place. For support with your own answers, see IGCSE Geography one-to-one tuition.