Choropleth Maps
A choropleth map is a map that uses different colours or shades to show how a variable, such as population density or unemployment rate, varies across geographical areas. Darker or more intense shading usually represents higher values, and lighter shading represents lower values, with a key explaining what each shade means. In GCSE Statistics, choropleth maps are used to display and compare regional data at a glance.
Method
- Look at the key (legend) first to see what each colour or shade represents.
- Note whether the shading uses a single colour with varying intensity or moves through different colours, since multiple hues can be harder to order by value.
- Identify the darkest and lightest regions to find the highest and lowest values on the map.
- Check whether the class intervals in the key are equal in width; unequal intervals can make regions look more different than they really are.
- Compare regions and describe the overall pattern, for example which parts of the map are consistently darker or lighter.
- Comment on any limitations, such as the map showing only one value per area and not the variation within it.
Worked example
A choropleth map shows unemployment rate by region using four shades: white = 0-2%, light grey = 2-4%, dark grey = 4-6%, black = 6-8%. Region A is shaded black, Region B is shaded dark grey, Region C is shaded white, and Region D is shaded light grey. (a) State which region has the highest unemployment rate. (b) Estimate the unemployment rate range for Region D.
- Read the key: black represents the highest class shown, 6-8%.
- Region A is shaded black, so Region A has the highest unemployment rate on the map.
- Region D is shaded light grey.
- From the key, light grey corresponds to the class 2-4%.
- Final answer: Region A has the highest unemployment rate (6-8%); Region D's unemployment rate is between 2% and 4%.
Practice questions
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Q1What is the purpose of the key on a choropleth map?Show answer
Answer: It shows what each colour or shade on the map represents.
Q2On a choropleth map shaded from white (lowest) to black (highest), a region is coloured mid-grey. What does this suggest about its value?Show answer
Answer: It has a middle (moderate) value, between the lowest and highest classes shown.
Q3Give one limitation of choropleth maps.Show answer
Answer: They show only one value for a whole area, hiding any variation within that area.
Q4A choropleth map uses class intervals of 0-10, 10-30, 30-40 and 40-90. Why might this be misleading?Show answer
Answer: The class widths are unequal, so shading intensity does not change proportionally with the data, making some differences look bigger or smaller than they really are.
Q5Two neighbouring regions on a choropleth map are shaded the same colour. What can you conclude about their values?Show answer
Answer: Both values fall within the same class interval, not that they are exactly equal.
Q6A choropleth map of rainfall uses two different hues (for example yellow to red) rather than one hue getting darker. Why can this style of shading be a problem?Show answer
Answer: Different hues do not have a natural order of 'more or less' like a single darkening shade does, so it can be hard to judge which colour represents a higher or lower value without constantly checking the key.
Exam-style questions
Written in the style of a GCSE Statistics exam paper, with a full mark scheme.
A choropleth map shows average house prices by region, shaded from light (low price) to dark (high price). Region X is shaded darker than Region Y. State what this tells you, and give one reason the map might not show the full picture.
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The table shows the percentage of households with broadband access in four regions: Region 1: 55%, Region 2: 78%, Region 3: 90%, Region 4: 62%. A choropleth map will use these class intervals: 50-60% (lightest), 60-70%, 70-90%, 90-100% (darkest). State which shade class each region should be given.
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A choropleth map compares the percentage of adults who smoke across five regions, using five equal class intervals. A student claims that because Region P's shaded area on the map is physically larger than Region Q's, Region P must have a higher smoking rate. Evaluate this claim, and describe two features that can make a choropleth map easy to misread.
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See real GCSE Statistics past-paper questions, with official mark schemes →
Free printable worksheet
Want more practice on paper? Download the choropleth maps worksheet pack - 14 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
This topic is chapter 24 of GCSE Statistics Foundation Workbook 1 and chapter 28 of GCSE Statistics Higher Workbook 1, the whole course as one free printable PDF.
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