While this map has been used several times to claim a ‘landslide’ victory for the Republican candidate, it is actually rather useless, as it completely ignores the fact that the overwhelming majority of Americans lives in the cities near the Upper East Coast (New York, Washington, Boston,…), near the Great Lakes (Chicago, Detroit), the West Coast (Los Angeles, San Francisco, Seattle), or in Florida. In short: land area does not equal population. While a map like this one is not strictly lying, it is (intentionally or not) hiding the fact that the split between Republican and Democratic votes was nearly 50–50.

Many of the maps published during this coronavirus crisis suffer from a similar problem. Take for example this map by ABC News showing the countries where COVID-19 cases have been confirmed:

Although somewhat helpful, such a map may say more about how connected a country is to the rest of the world, rather than showing how the virus has spread. In any case, it does not provide information about the number of cases. From this map on March 10, we cannot deduct that there was only one confirmed case in Burkina Faso, but over 10.000 in Italy, and over 80.000 in China.

A typical approach to avoid this issue are choropleth maps, a complicated name for something very simple. Blame the Greeks, choros means ‘region’ and plethos means ‘multitude’, hence the name. My scientific brain always tricks me into saying ‘chloropleth maps’, probably because it thinks about chloroplasts in plant cells. But don’t get your hopes up, there’s no connection at all — just my stupid brain. The ‘chloro-’ in chloroplasts also comes from Greek, but from chloros, ‘green’. The same origin, it turns out, as chlorine (because of its pale green color) or chloroform (which contains chlorine). But my apologies, I digress… I might have been reading too much Stephen Fry lately, who would probably love this kind of etymological exploratory ramblings.

So, a choropleth map. In such a map, regions are again colored, but the value of the color (lightness or darkness) depends on the underlying parameter, for example the number of infections in a country. In its most basic form it looks like this example by CNBC:

Choropleth maps can be particularly helpful in comparing different counties or regions within a country, such as this map by CNN:

However, choropleth maps have their own unfortunate downsides and pitfalls. I will not go into much detail here, as everything was already written down excellently by ‘cartonerd’ Kenneth Field. Let me just summarize:

• choose your colors or color scheme responsibly,
• choose your categories responsibly, and
• use relative numbers to avoid population density distortion.

Or, just maybe, a bar chart might be a better choice:

Another limitation of choropleth maps is that small nations or regions are nearly impossible to see. Again, area size is messing up our ability to interpret the map correctly. For example, try to find the number of cases in Singapore, Luxemburg or Barbados on the maps of Our World in Data:

Bubble maps, such as the ones by the Washington Post shown above, avoid this trap because each nation gets its own bubble, independent of area, population, or population density. This is what makes this kind of chart so successful to map a wide range of values in a wide range of countries around the globe.

There is only one minor downside: bubbles can start overlapping each other when two neighbouring regions have very large values (or one of them has a large value while the other only a small one). Then your bubble chart might start looking like this:

Not particularly helpful, I’m afraid… There is no perfect solution to avoid this, but play around with the opacity of your bubbles, be clever with bubble outlines, and the result might be both beautiful and effective:

I already hinted earlier that in some cases, a simple bar chart might be a better option than a complicated map. As Leonardo Da Vinci said: “Simplicity is the ultimate sophistication” (except that he never said that). Another simple but effective alternative might just be… a table.

Many great examples can be found, including the Washington Post ones at the beginning of this chapter, but I was particularly charmed by the Datawrapper ones by Lisa Charlotte Rost, with a clever use of color to bring a touch of optimism to this heavy subject matter:

Okay okay, not everything is perfect when using tables. For example, they can also be used to misinform, or at least to distort information or present data in a way that suits you best. For a while, the following table was popular on social media in the Netherlands, showing how the country was following the exact same pace as Italy, with only a few weeks of delay. Panic!

However, it was intelligently shown by RTL Nieuws (in Dutch) that the situation looks completely different when you choose different dates to start the comparison, such as the date of the first death:

Also, differences in age distribution among the population have an impact on the death rate, so it’s rarely a good idea to blindly start comparing different columns or rows with each other, without thinking things through. Remember: if creating panic is your goal, you will always find some data somewhere presented in such a way that you can do so.

There are many, mány more amazing things you can do with tables, also in coronavirus times, but that will be something for another chapter!

To end this chapter on a lighter note, let’s just have a look at some garbage maps from around the web. Starting with the Daily Mail committing some serious data visualization crimes, showcasing what Andy Kirk aptly calls ‘the Staircase from Hell’:

Metro sits in the same boat, but at least they blow up the map of Europe to ensure that poor San Marino isn’t left out: