GDP growth rate and public debt (4)

Exploring GDP growth rate and debt to GDP ratio


Exploring GDP growth rate and debt to GDP ratio (See the code)

This analysis is a departure from the investigation of MPs expense claims I’ve been doing recently. I was inspired to create these visualisations when I saw this article by I really liked the idea of what they were exploring, and thought that there were some great things about this visualisation, but that there was also some room to make it clearer.

I like that the countries are positioned where they would be on a globe. The colour scale is sensible, and the idea of changing the scale of the countries to show their debt-to-GDP ratio is great; I just find it hard to understand how large the countries should be with no reference point. For example, I can tell that China and Japan are wildly different in size than they would be on a real globe, however I don’t really have much idea of the relative sizes of Ireland and Iceland.

I thought it would be fun to try to reimagine this chart without using a map to show the size of the debt-to GDP ratio. In doing so, I created three different charts of varying quality and clarity, and this blog post discusses the positives and negatives of those charts. You can see how I got the data and made the charts here.

The first chart

I set myself the challenge of creating a categorical scatterplot (scattergorical plot?), as I quite like the look of them. I wanted to retain the idea of displaying one aspect of the data by varying the size of a data point and so began by creating a bubble plot.

On this chart, the countries are grouped by which geographical region they are in. The debt-to-GDP ratio is displayed on the vertical axis, and the bubbles are sized to display the GDP growth rate. We can see that Ireland (the biggest blue circle), whilst it has a debt-to-GDP ratio of over 100%, also has a high GDP growth rate. Italy and Portugal (the two smaller blue circles to the right of Ireland) on the other hand  have similar ratios of debt to GDP, but much smaller GDP growth rates. This might suggest that their debt is less sustainable than Ireland’s, although there are many more factors at play here.

From this chart, we can see that the country in the worst position is Japan (the dot at the top-right corner). Japan has a debt-to-GDP ratio of nearly 250%, and a very small GDP growth rate (it’s actually negative! Find out how I fixed this problem when creating the chart). This demonstrates one of the things that I dislike about this chart; whilst it’s quite pretty and all the information is available to interpret it, the chart just isn’t intuitive to understand.

First of all, displaying the growth rate as a size is not particularly helpful – a growth rate is a measure of speed; this should be on the x-axis because we (generally) experience acceleration horizontally, rather than as an increase in size . . .

Secondly, because the plot looks like a scatterplot, our instinct is to look for a relationship between the two variables – whilst I’ve aimed for a categorical scatterplot, I don’t think I’ve quite achieved it.

The second chart

I thought I’d continue with the scatter theme and see if I could get some mileage from it. This is my least favourite chart, but there are some good points. I like that the growth rate is shown on the x-axis, and that countries with negative growth rates can be easily distinguished (not the case with the previous chart), but I really don’t like that the countries aren’t immediately identifiable. Without the hover action, any reader would be absolutely perplexed by what the different dots represent.


The final chart

So this chart presented some technical difficulties, but I managed to work round them to create what I think is the better of the three charts.

I went with the scattergorical theme, but used the lines to give the impression that the user is looking at a horizontal bar chart. I set the growth rate on the x-axis, and as a result it’s really easy to see which countries have a negative growth rate. The bubbles are sized for the debt-to-GDP ratio, which I think works quite well. This chart allows the user to not only see the extreme cases, but also to more easily compare countries within the regions.

The most striking thing about the data here is that some countries appear to be in trouble (by this measure at least). Argentina, Finland and Italy all have negative growth rates, although Argentina has a relatively small public debt as % of GDP. Japan on the other hand has fairly stagnant growth, but a it’s public debt as a percentage of GDP is huge compared to other countries in this chart. Finally, I think the variation within Europe is also very striking – it would be nice to have more complete data to see if this variation exists within other regions as well.

Thanks for reading! You can find more data visualisation tutorials elsewhere on my my blog. You can fork this project at my Github, or follow me on Twitter to keep up to date with new visualisation tutorials.

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