Thematic World Maps for Mobile

Why are we still designing maps for the wrong screen?  — 

Most world maps you see online are not really designed for mobile screens. They're too small and require interaction to see countries like Switzerland. At NZZ, we wondered if we could come up with a design that works better. In a large user study, we showed that our redesigned world map improves readability – especially for small countries. We also found that using bubbles sized according to population, rather than land area, led to interpretations that more accurately reflected the underlying data.

Read the full paper

Forced interaction

This world map is too small, how can I zoom in?

If you’ve ever read a news article on your phone, you’ve probably asked yourself this. Maybe the map showed COVID-19 prevalence or greenhouse gas emissions. Either way, small countries like Switzerland and Singapore were nearly impossible to spot without pinching, tapping, and dragging.

Maps Aren’t Built for Mobile

The world map you see everywhere today is based on a design from the 16th century – originally printed on scrolls and used for navigation. We’re so familiar with its shape that even in the smartphone era, few dare to deviate from it.

Three Smartphones showing world maps from different news outlets. The New York Times, Die Zeit and the Guardian

It makes sense that major news outlets stick to familiar visual formulas. But we were surprised that even within the cartographic community, there has been little experimentation with formats better suited to vertical screens.

Beyond the inefficient use of mobile screen space, online publications also lean heavily on choropleth maps to show population-related data – like “Per capita CO₂ emissions from domestic aviation.” This is despite decades of research showing how choropleths distort perception. These maps give visual weight to large, sparsely populated countries like Russia or Australia, while minimizing countries like Bangladesh or the Netherlands. The result? Readers walk away with a skewed impression. In this example, readers are likely to strongly overestimate emissions from domestic aviation as you can see in the comparison.

The first map is a choropleth from Our World in Data. The second map shows the exact same data with the same color scheme but uses bubbles that are sized according to country population. The first map would lead one to overestimate emissions from domestic aviation

Yes, this is a pointed example – but it happens more often than you might expect, once you start paying attention. A world map drenched in red leaves a very different impression than one that’s mostly orange.

Rethinking Thematic Maps

With these issues in mind, we set out to redesign thematic maps at NZZ. The challenge became especially urgent during the COVID-19 pandemic, when demand for global maps spiked. As a first step, we identified two dominant types of thematic maps in our reporting:

  1. Glorified Lists – These maps essentially act as visual lists, often displaying categorical data (e.g. NATO membership or travel rules). They are not designed to reveal regional or global patterns – their main advantage is that they make it easier to locate countries quickly than a textual list.

  2. Spatial Distribution Maps – These maps are intended to show regional patterns, such as climate impacts or vaccination rates. When visualized with choropleths, they often mislead by tying visual weight to land area rather than population.

We tailored a different map for each of these purposes. We call the first one split continents and the second one bubblemap:

On the first map, continents are split and resized to make small countries easier to see. The second map uses bubbles scaled to population, giving more populous countries greater visual weight.

The Test: Do These Designs Actually Work?

To test our approach, we recruited 333 NZZ readers. First, we asked them to find small countries on the “glorified list” design and report their color. The result: 87% got it right, compared to 72% on the baseline map. This suggests that even when continents are rearranged, people can identify countries – so long as their shapes remain familiar.

To test the Bubble Map, we asked readers to estimate the map’s “mean color” – a perceptual task that research suggests is difficult, but doable.[1] Accuracy was low overall (31%), but it was still a notable improvement over the choropleth baseline (20%). In other words, the bubble map delivers a truer impression straight to the reader’s visual system.

The first two maps show the variants used to test our glorified list design. The second pair was used to evaluate the bubble map.

The Aftermath

Still, many readers commented that the bubble map was hard to read. A few added that it was more informative, but overall, the map remains unpopular. We've received similar feedback internally, even when the reasoning behind the design is explained.

Clearly, the bubble map isn’t the final word. We're still exploring how our maps can strike a better balance between perceptual accuracy and visual familiarity. If you are interested in the details you can read the full paper. I’d also love to hear how others are approaching the same challenge.

  1. D. A. Szafir, S. Haroz, M. Gleicher, and S. Franconeri, “Four types of ensemble coding in data visualizations,” Journal of Vision, vol. 16, no. 5, p. 11, Mar. 2016. ↩︎