How should we visualise inequalities in household wealth?

The Office for National Statistics releases a biennial report on wealth distribution in Great Britain, which visualises household wealth distribution in a number of different ways. In this post I consider some of the strengths and limitations of some of these visualisations, and if it’s desirable, or even possible, to settle on one ‘best type’ of wealth inequality visualisation?

The data discussed below is taken from the fifth wave of the Wealth and Assets Survey covering the period July 2014 to June 2016

The top 10% compared to ‘middle 40%’ and the bottom 50%

Here we learn that the top 10% of households have nearly as much as the other 90% put together, while the poorest 50% have only 10% of the wealth (rough figures)

This way of displaying wealth inequalities lends itself to a pie chart which The Inequality Trust produced for the previous wealth survey (broken down further)….

The pie chart is useful because you can see immediately that the richest 10% of the population have nearly half of the total wealth, or nearly as much as the other 90% put together. The problem is it doesn’t show you clearly how many times richer, a good old basic bar chart is much better for this.

Displaying total household wealth by percentile points

Here we get the really stark contrast… top 1% of households have total wealth of £3,227,500 or more. The poorest 1% of households have negative wealth, so you cannot even make a comparison!

 

The strengths of this type of visualisation are that it’s very easy to see the stark differences between not only the top and the bottom, but also the top and the median, and it’s quite easy to mentally group these into deciles – the bottom ten clearly have almost no wealth, however this ‘mental exercise’ only makes sense for the first 9 deciles, to so for the top ten percentiles would lose site of the massive differences between the very richest and even the average here.

The downsides of this are that the huge wealth of the top 1% makes the scale too large to show meaningful differences lower down, also you can’t really show further data within each group, as you can do with deciles…

Displaying aggregate total wealth by declines, broken down my wealth type

 

This is showing you something different than the above – you take all the wealth of the households in that decile and add it up, and you learn that…

  • The richest 10% of households (the top 2.5 million) have wealth of £5.5 trillion
  • The poorest 10% of households (the bottom 2.5 million) have combined wealth of £5 billion
  • In other words the riches 10% are 1000 times richer than the poorest 10%.

What I like about deciles is that it’s so much easier on the brain – visually it’s just so much easier to make a comparison. This is why it’s possible to add in another layer of data by colour coding the different wealth types, which also gives more granularity.

However, the problem is that you lose that top 1% skew, and you also lose the negative wealth (debt) of the bottom percentiles.

NB the contrast here seems greater than with the percentiles above, that’s usually not the case, but that’s because of the enormous figures involved (measuring something different).

Is there a ‘best way’ to display inequality data?

The techniques used to display the data could influence how people feel about wealth inequalities. For example, presenting the data in deciles makes the wealth inequalities seem greater, while presenting them in thirds, less so, and a bar chart shows the differences more starkly than a simple table or pie chart.

Where changes over time are concerned, using the Gini coefficient makes inequalities seem as if they have hardly changed at all, but comparing the changes in wealth by ‘households by income decile’ (admittedly confusing to get your head around at first), we see that the poorest 30% of households have gained no wealth, while the richest 20% have gained more than everyone else.

It’s quite possible (even likely) that someone’s politics could influence their decision over how to visualise inequality data: and you would probably expect those that are against inequality to prefer those visualisation techniques which show the most dramatic differences, in the hope that these would inspire a sense of social injustice in people.

For those on the political right, and working within government, you would perhaps expect them to favour visualisation techniques which show the lowest levels of inequality, or even obscure visualisations which contain so much information you’re not actually sure what’s going on. For an interesting example of a publication which seems to do this, have a look at the ONS’ latest publication on income inequalities, it is nowhere near as clear as the one I’m talking about here on wealth inequalities.

To my mind it’s impossible to come to a truly objective decision about the most valid way to display wealth inequality data – whether you display the data broken down into five quintiles, or ten deciles, or whether in a bar chart or a pie chart is going to depend on what aspect of the data you’re focussing on, which in turn depends on the story you’re trying to tell, or what you ultimately want to do with the data. And then of course, you also have to please the people that are paying you to write the report.

Given that it seems unlikely that we’re going to get a totally value-free representation of wealth (or any other type of) data, it would seem to make sense for the ONS to move towards developing interactive infographics which the user can manipulate, so they can display the data in a means they want to. Interactive infographics allow the user to determine their own measures of wealth, their own bins (groups), and their own timescales, and allow them to hide any data they don’t want to see so as to make comparisons easier.

However, a potential problem with this is that it encourages a postmodern, voyeuristic attitude to statistics on wealth inequalities… the more magnificently flexible the infographic, the more bells and whistles, the more the user becomes enraptured by playing around with the different options. The effect of this may be to render an important political issue neutral.

Sources 

Wealth in Great Britain Wave 5: 2014 to 2016: Main results from the fifth wave of the Wealth and Assets Survey covering the period July 2014 to June 2016

The Inequality Trust.

 

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