What Is a Cartogram?

A cartogram deliberately changes the size, shape or arrangement of geographic units according to a variable such as population, votes or GDP. Geography is distorted on purpose so that the mapped variable—not land area—controls visual prominence.

A country with a large population can become much larger than its conventional outline, while a physically large but sparsely populated country can shrink.

Why distort geography deliberately?

Conventional maps give more page space to places with more land area, which can be undesirable when land area is irrelevant to the subject.

A population cartogram asks the reader to see the world in proportion to people rather than square kilometres. An election cartogram can resize regions by electorate, making the visual footprint correspond more closely to the number of voters represented.

The distortion is therefore the method, not an error.

Main cartogram types

A contiguous cartogram keeps neighbouring units connected while deforming their shapes and sizes. A non-contiguous cartogram, by contrast, scales units independently, allowing gaps to appear between them; shapes can remain more recognisable, but adjacency is less visually direct. A Dorling cartogram goes further by replacing geographic areas with circles or other simple symbols sized by the variable and positioned approximately according to geography.

Each form preserves and sacrifices different aspects of spatial recognition.

What cartograms reveal

Cartograms are powerful when conventional area would otherwise dominate the map. They can make small but populous or economically important regions visible and large sparse regions less visually overwhelming.

They are also useful for questioning an assumption built into ordinary maps: that physical land area deserves the same visual importance as the subject being discussed.

What they sacrifice

Cartograms make ordinary location, shape, distance and area harder to read, so a reader unfamiliar with the geography may struggle to identify regions after strong deformation.

For this reason, labels, reference outlines, companion maps or interactive transitions can be helpful. A cartogram often works best when the audience already has some geographic context or when a conventional reference map is available nearby.

Where cartograms can mislead

A cartogram can look authoritative while hiding how the transformation was generated. Extreme values can produce shapes that are difficult to recognise. Small areas can disappear visually. Readers may interpret adjacency or distance more literally than the transformed geometry warrants.

The variable itself also needs the same scrutiny as in any other map, since resizing regions by a poorly chosen statistic does not become meaningful merely because the result is visually striking.

When should you use one?

Use a cartogram when land area creates a misleading visual hierarchy and deliberately rescaling geography helps communicate the subject.

Avoid it when accurate shape, distance, local position or navigation matters. A cartogram is not a general replacement for a geographic map; it is an argument about which quantity deserves space.

Cartograms change the visual denominator

A conventional political map gives land area the visual denominator, so large territories occupy more of the page. A cartogram replaces that denominator with another variable: in a population cartogram, visual space is allocated according to people; in a vote cartogram, it may be allocated according to electorate or votes cast.

That shift can expose how strongly ordinary geographic area shapes perception. It can also make comparison with familiar geography harder, which is why cartograms often work best alongside a conventional map rather than as the only geographic reference.

The transformation method matters

Different cartogram algorithms preserve different properties: some prioritise contiguity, some approximate shape, and some abandon original polygon geometry for circles or squares. Two cartograms built from the same variable can therefore look materially different.

When the exact transformation supports an analytical claim, document the method. For editorial illustration, it may be enough to identify the cartogram type and the variable controlling size, but the map should never imply that the distorted geometry is suitable for ordinary distance or area measurement.