Thematic map
A map focused on one data theme or variable.
What Is a Cartogram in AP Human Geography?
A cartogram is a thematic map that intentionally changes the size or shape of regions to represent a data variable. On a cartogram, larger regions usually mean larger values, such as higher population, GDP, votes, emissions, or disease burden, not larger land area.
Memory Shortcut
Cartogram = size shows data.
- Land area is distorted.
- The variable controls size.
- Bigger shape means bigger value.
- Use the title and legend before interpreting.
Start Here: How to Use This Cartogram Guide
- Learn that cartogram distortion is intentional.
- Identify the variable controlling region size.
- Compare cartograms with choropleth and reference maps.
- Practice explaining one strength and one limitation.
- Finish with MCQs, flashcards, and FRQ practice.
Cartogram Definition
A cartogram is a thematic map that resizes or distorts places based on a data variable. Instead of showing true land area, the map changes region size to show values such as population, GDP, votes, emissions, or disease cases. Cartograms help students see geographic patterns that might be hidden on a normal land-area map.
Intentional distortion
The map changes size or shape on purpose to represent data.
Data variable
The value controlling the size of each region.
Magnitude
The size or amount of the mapped value.
Land-area comparison
Cartograms often challenge what normal maps make visually dominant.
Cartograms are one type of thematic map in Maps and Map Interpretation. Pair this guide with all AP Human Geography map types, introduction to maps, and map purpose and geographic questions.
How Cartograms Work
Cartograms begin with geographic regions and a data variable. The mapmaker resizes each region so its area or symbol size reflects the data. A country with a large population may appear larger than its actual land area, while a large but sparsely populated country may shrink.
AP Exam Tip
On a cartogram, do not interpret size as land area. Interpret size as the mapped variable.
Cartograms are built from quantitative data and spatial analysis tools — the same skills you practice when reviewing scale of analysis and distribution patterns in Unit 1.
Types of Cartograms
Cartograms come in several forms. Each type balances shape recognition, adjacency, and clean value comparison differently.
Contiguous cartogram
- Definition
- Regions remain connected but shapes are distorted.
- Best for
- Showing a variable while keeping adjacency.
Non-contiguous cartogram
- Definition
- Regions keep their general shape but are resized and separated.
- Best for
- Showing comparison while preserving recognizable shapes.
Dorling cartogram
- Definition
- Regions are replaced with circles sized by data.
- Best for
- Clean value comparison when shape is less important.
Value-by-area cartogram
- Definition
- Area is scaled directly to a mapped value.
- Best for
- Population, GDP, votes, or disease burden.
Election cartogram
- Definition
- Regions are resized by votes, seats, or population.
- Best for
- Showing political results without overemphasizing land area.
Real-World Cartogram Examples
These examples show how cartograms reveal magnitude patterns that land-area maps can hide.
Population cartogram
- Variable
- Total population.
- Pattern
- Highly populated countries or cities enlarge.
GDP cartogram
- Variable
- Gross domestic product.
- Pattern
- Economically large regions enlarge.
Election cartogram
- Variable
- Votes or electoral seats.
- Pattern
- Dense voter regions become visually larger.
Carbon emissions cartogram
- Variable
- Total emissions or emissions per capita.
- Pattern
- High-emission regions expand.
Disease burden cartogram
- Variable
- Cases or deaths.
- Pattern
- Hard-hit regions enlarge.
Internet users cartogram
- Variable
- Number of users.
- Pattern
- Large digital populations expand.
Migration cartogram
- Variable
- Migrant population or flows.
- Pattern
- Major origin or destination regions enlarge.
Urban population cartogram
- Variable
- Urban residents.
- Pattern
- Large urban regions dominate the map.
Compare cartogram examples with choropleth maps and dot distribution maps when you study data reliability and bias in Unit 1.
Cartogram vs Other Map Types
| Map Type | Symbol System | Best For | AP Trap |
|---|---|---|---|
| Cartogram | Distorted size or shape | Data magnitude where land area misleads | Thinking distortion is an error. |
| Choropleth map | Color shading by region | Rates or percentages by area | Hiding internal variation. |
| Reference map | Accurate location and orientation | Finding places and features | Assuming it explains a data pattern. |
| Dot distribution map | Dots | Clusters and concentration | Assuming exact locations. |
| Graduated symbol map | Different-sized symbols | Raw counts at point locations | Confusing symbol size with land area. |
Cartogram vs choropleth
Cartograms resize regions based on data, while choropleth maps keep region shapes and use color shading.
Cartogram vs reference map
Reference maps preserve location and shape for orientation. Cartograms prioritize data comparison over geographic accuracy.
Cartogram vs graduated symbol
Graduated symbol maps use sized symbols at point locations. Cartograms change the size or shape of regions themselves.
Also review map scale and generalization, map projections, and isoline maps when you compare map families across Unit 1.
Why Cartograms Distort Space
Cartograms distort space because normal land-area maps can mislead viewers. Large land areas can look important even when they have fewer people, fewer votes, or lower economic activity. Cartograms make the data variable visually dominant.
Example: On a normal world map, Canada and Australia appear very large. On a population cartogram, they shrink because their populations are smaller than countries such as India, China, Indonesia, or Nigeria.
AP Exam Tip
A cartogram's distortion is the message. The map is not broken; it is emphasizing a variable.
Distortion connects to broader Unit 1 ideas in spatial concepts and the Unit 1 Thinking Geographically hub.
Strengths and Limitations of Cartograms
Strengths
- Makes data magnitude visually clear
- Reduces land-area bias
- Strong for population and election data
- Makes surprising patterns memorable
- Useful for comparing totals
- Helps challenge assumptions from reference maps
Limitations
- Distorts shape and distance
- Can be hard to recognize regions
- Poor for navigation
- May confuse readers unfamiliar with cartograms
- Usually emphasizes one variable at a time
- Requires careful legend/title reading
Common Cartogram Mistakes
Thinking distortion is an error
Fix: Distortion is intentional and represents data.
Reading size as land area
Fix: Size represents the mapped variable.
Skipping the title
Fix: The title tells what variable controls size.
Confusing cartograms with choropleths
Fix: Cartograms resize regions; choropleths shade regions.
Using cartograms for navigation
Fix: Cartograms are poor for exact location and distance.
Forgetting the legend
Fix: The legend explains what size means.
Assuming every cartogram uses the same method
Fix: Contiguous, non-contiguous, Dorling, and value-by-area cartograms look different.
Describing without explaining
Fix: After describing which regions enlarge, explain what the variable means.
AP Exam Strategy for Cartograms
In MCQs
- Identify the map type.
- Read the variable controlling size.
- Explain why land area is distorted.
- Compare cartograms with choropleths.
- Recognize that bigger shape means bigger value.
In FRQs
- Define cartogram.
- Identify the variable.
- Describe which regions enlarge or shrink.
- Explain why distortion helps show the pattern.
- Explain one limitation.
Variable → Distortion → Pattern → Explanation → Limitation
Example: The cartogram resizes countries by population. India and China appear larger because they have very large populations, while Canada shrinks because its land area is large but its population is smaller. The cartogram helps reduce land-area bias, but it distorts shape and distance.
Cartogram stimuli connect to AP Human Geography themes such as population, elections, development, and environmental data across Unit 1 and later units.
Cartograms FRQ Practice
Prompt: A world population cartogram resizes countries based on total population.
- A. Define cartogram.
- B. Explain why India and China might appear larger than their land area on a population cartogram.
- C. Explain one limitation of using a cartogram.
Suggested answer:
A. A cartogram is a thematic map that distorts the size or shape of regions based on a data variable.
B. India and China would appear larger because their populations are very large, so their map size increases to represent the population variable rather than land area.
C. A limitation is that cartograms distort shape, distance, and location, making it harder to use them for navigation or exact geographic orientation.
Rubric
- Part A: Must mention data variable and size/shape distortion.
- Part B: Must connect enlarged size to population value.
- Part C: Must explain a valid limitation such as distorted shape, distance, location, or recognition difficulty.
Cartograms Practice Questions
Use these cartogram practice questions to test whether you can identify cartograms, read distortion, compare map types, and explain cartogram limitations.
Cartograms Flashcards
Use these flashcards to review cartogram definitions, types, examples, comparisons, limitations, and AP exam traps.
Continue the Maps and Map Interpretation Path
Previous TopicIsoline MapsParent HubMaps and Map InterpretationNext TopicMap ProjectionsPracticeUnit 1 Practice QuestionsFRQ PracticeUnit 1 FRQ Practice
Return to the Maps and Map Interpretation hub, Unit 1 Thinking Geographically, or Unit 1 practice questions. Related map guides: Choropleth maps · Dot distribution maps · Isoline maps · Reference vs thematic maps · Map types overview.
Also review introduction to maps, map purpose and geographic questions, spatial concepts, map projections, and map scale and generalization to strengthen your Unit 1 map mesh.
Cartograms FAQ
What is a cartogram in AP Human Geography?
A cartogram is a thematic map that intentionally changes the size or shape of regions based on a data variable such as population, GDP, votes, emissions, or disease cases.
What is a simple example of a cartogram?
A population cartogram is a common example. Countries with large populations, such as India or China, appear larger, while countries with large land area but smaller populations may shrink.
Why are cartograms distorted?
Cartograms are distorted on purpose so region size represents a data value instead of true land area.
What does a cartogram show?
A cartogram shows the magnitude of a data variable by resizing places, making larger values appear larger on the map.
Are cartograms thematic maps?
Yes. Cartograms are thematic maps because they focus on one data theme rather than accurate location, distance, or shape.
What is the difference between a cartogram and a choropleth map?
A cartogram resizes regions based on data, while a choropleth map keeps regions the same shape and uses color shading to show values.
What is one weakness of cartograms?
A weakness of cartograms is that they distort shape, distance, and location, which can make places harder to recognize or use for navigation.
How should I read a cartogram on the AP Human Geography exam?
Read the title and legend first, identify the variable controlling size, describe which regions enlarge or shrink, explain the pattern, and mention one limitation.