One region is desert, only 10,000 people live there and unemployment rate is 20%.
In the other region there are 1M people and the employment rate is 3%.
Now if you look at the map, it seems that the country is doing pretty poorly. Half of the country has a bad employment rate. Whereas in reality it only affect a small portion of the population.
> In the other region there are 1M people
This has already been normalized: these are European NUTS-2 regions, which are drawn to contain roughly equal populations. Each NUTS-2 region is supposed to be 800k to 3 million people per region. It's not perfect, but it's not just geographical borders with wildly different populations.
For example, London is split into 5 regions, most big cities are their own region, and small countries are just one region. Going into even smaller regions would be nice (and are defined in the standards as well), but it seems that nobody has put in the effort to collect data at that granularity.
It's far from perfect in some countries. The Community of Madrid with 6.5 million people is its own region (or Catalonia with 7.5 million); that's more than Scotland, which is cut up into five NUTS-2 regions. The Paris region (Île-de-France) has 12 million inhabitants, which is more than, say, Austria or Hungary or the Czech Republic, each cut up according to more or less traditional geographic divisions.
You have a point according to how NUTS should work, the grandparent does have a bit of a point according to what it's like in practice.
No, the visualization is completely wrong to begin with, because areas with practically population zero like in the northern parts of Scandinavian countries are still comprised of the same regions as their southern neighbors, which makes absolutely no sense and increases their importance area-and-color-wise on the map.
It doesn't claim to be a map of 'unemployment rate confounded with population density' in the first place. You've imagined that. It's a map of simply the 'unemployment rate'.
This area is not very significant in terms of number of people, unemployed or not, but it is very visible on the map (also due to map projection which enlarges northern areas).
(The four NUTS2 regions in continental Finland have roughly the same population, the fifth one Ahvenanmaa/Åland has a population of 30,000 people).