Tag Archives: graphs

Bars to understanding

9 Nov

What’s going on with this graph in the Mail?

It says “Tory poll lead falls after standards row”, but it seems to show the Tories pulling well ahead of their hated rivals, the Tories, while Labour loses ground inexorably to the Labour party of last week.

Squinting at the small print, we discover that the lighter coloured bars represent the current polling, and the darker bars the previous week’s results. However, the later figures have been placed to the left of the earlier ones, not the right, in reverse chronological order – a methodology applied equally to all parties, but one which, visually, gives the opposite impression to what’s intended. It looks like a picture of continued blue success and red failure.

Similarly, what does this graph, from March, suggest to you is happening?

The correct answer is that the Tories have moved out to 45% of the vote and Labour has fallen back to 32%. But is that what you initially “see”? The Tories look to be declining and Labour surging. Isn’t it more usual to place the later figures on the right, as the eye tracks naturally from left to right across the page? And don’t the wide gaps between the different parties encourage you to compare their performance against themselves, rather than the opposition? Also, the brighter blue seems to count as a “dark” colour, but the brighter red a “light” one: going just by what’s most eyecatching, don’t you end up comparing 39% with 35% in the first graph and 45% with 36% in the second, neither of which represents the correct gap?

This isn’t some effort to obfuscate unfavourable findings, or try some Lib Dem-style sharp practice with the visuals: the Mail has been angered by the Owen Paterson/sleaze debacle, and first graph appears under this uncompromising headline:

It just seems that they always do them this way. But in the absence of any visible x-axis, readers are naturally going to read it from left to right, because that’s how nearly all x-axes run in every other graph. Why flip it for this?