A contender for 'The worst info graphic of 2011' award

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understandinguncertainty.org was produced by the Winton programme for the public understanding of risk based in the Statistical Laboratory in the University of Cambridge. The aim was to help improve the way that uncertainty and risk are discussed in society, and show how probability and statistics can be both useful and entertaining.

Many of the animations were produced using Flash and will no longer work.

iconWe may already have a winner for the 'Worst info graphic of 2011 award' with this panel which appeared in the Times yesterday (Jan 4th).

Worst info graphic?

A history of VAT in Britain

The diagram is clearly inspired by Florence Nightingale's 'Coxcombs', but there I'm afraid the similarity ends. Nightingale understood that the graphical impact of any sector was in its area and plotted her data accordingly. Our Times journalist however, is happy to subtract 4% from the VAT rates and plot that figure on a radius, helpfully highlighting the 8% rate within the 17.5% sector so we can fully appreciate what a tiny proportion 8% is of 17.5% (let alone 20%).

We feel that the misrepresentation of the data here far outweighs any wow factor from the unusual design. There's real political bias in the diagram too. It may not be intended, but it is there nonetheless. Remembering that area is proportional to graphical impact, and choosing units so 17.5% has area 100 we can even calculate how much!

Graphical impact of each VAT rate
VAT Rate Area (scaled so 17.5% is area 100)
20% 140
17.5% 100
15% 66
10% 20
8% 9

The VAT rise from 17.5% to 20% is made to appear like a 40% increase! That's really quite impressive.

Of course, many other media outlets have erroneously reported the increase as one of 2.5%. Very few reporters appear to be interested in the percentage increase in produce costs - which is 2.1% $= \frac{2.5}{117.5} \times 100$ or in the percentage increase in VAT - which is 14.3% $= \frac{2.5}{17.5} \times 100$.

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Someone on the wireless said that 20% was the highest rate of VAT ever. That is true, but I can remember its predecessor, purchase tax, reaching 36%. I think it happened while James "The Stoker" Callaghan was Chancellor of the Exchequer but I'm not sure. That would make it 1964 to 1967.

Why on earth didn't they just use a bar chart with time on the x-axis? That would have enabled easy comparisons between years.

I think the area figure for 20% VAT in your table above should be 140 rather than 143. But your point is still very much valid - the graphic is eye-catching, but the author should have smelt a rat when comparing the microscopic 5% with the massive 20%!

Well spotted - you're right. I've corrected the article now.

Everyone has now forgotten the "luxury" rate of 25% which applied for a few years - possibly the dying days of the Callaghan government. So we're not quite at the highest rate today (due to changes in spending patterns, much of what today counts as normal household expenditure - TVs, computers, recorded music, etc - would back then have qualified as luxury). Jim Roberts