Further adventures in treemapping the UK's migrant population

9 Apr 2016 14:05 GMT

Earlier this week I posted a treemap showing the UK's migrant population by country of birth. A common reaction among people who saw it was to wonder what the size of the UK's foreign-born population was relative to the size of the UK-born population.

To help put that in context I have produced a new nested treemap showing the population of the UK broken down by region and broad country of birth. The population in each region is grouped into those born in the UK, those born in other EU countries, and those born in countries outside the EU.

While it's interesting to see the data visualised in this way, the advantages of using a treemap rather than a traditional bar chart are much less obvious in this case. When showing the migrant population by individual country of birth, a treemap lets you compare data for a very large number of countries in a way that is much easier to gloss than a bar chart. It allows you to group countries into common geographical regions, which represent the group's aggregate size. And the arrangement of countries from largest to smallest in each group provides a good visual representation of the distribution of the population within the group.

In this case, the UK's migrant population is too small as a proportion of the total population to break down into individual countries of birth, or anything more than two or three groups. Arguably the most interesting thing about the visualisation is how small the migrant population appears relative to the size of the UK-born population in every region outside London. On the other hand, a treemap makes it harder to make exact comparisons between the size of the migrant population in each region.

In short, I don't think this treemap is as effective as the last one, but that is probably because it is less well suited to the data being presented. But the new version of D3 made it just as easy to produce this treemap as the last one, and I thought it was worth sharing for those that asked to see it.