How not to visualize Coronavirus data

Hungary’s Surgeon General published a map today titled “Affected municipalities and age distribution of infected people”. It is really bad.

The following map was published today on the official Coronavirus site of the Hungarian government.

Map showing “Affected municipalities and age distribution of infected people”. Source.

The map shows all municipalities in Hungary. As the note on the bottom explains, municipalities that had at least one (known) Coronavirus infection since March are shown in red, the ones with no infection yet are shown in green.

Putting aside the fact that the map has no information whatsoever regarding the “age distribution of infected people”, this is still a terrible map.

1. Using red and green as colors to show information is bad for accessibility: people with red-green color blindness cannot distinguish these colors.
2. There is no good reason to use dots for each municipality (that even overlap each other) instead of a choropleth map, where the geographical area of each municipality would be colored based on some metric.
3. This binary metric does not really offer any insight: what do we learn from the fact that there was at least one infected person in a town? Instead, the metric we should use is the number of cases per 100000 inhabitants as this would tell us how bad the situation really is in a given location.

Choropleth map of Hungary showing population density on the district level. CC-BY-SA 4.0 by Klarigi. The Hungarian government does not release detailed Coronavirus data, therefore I can only add an illustrative map here instead of one showing real data.

In addition to these problems, in my opinion, posting a static image instead of an interactive map on a government website in such a situation is inexcusable. One can use Leaflet or D3.js to create whatever interactive map they want, or, if they do not have that expertise in the team, they can just create interactive maps with free online tools, such as DataWrapper.de.

The Atlo team, a group of data journalists maintains a much better dashboard than this simple map by keeping track of the government’s daily announcements. However, since this is still just a few data points, the highest granularity available there is still on the county level. A government does not need a group of volunteers to do its job though. For example, the Dutch government has a detailed, interactive (and user friendly) Coronavirus dashboard that is updated daily.