Blog reader Matt Raven has drawn my attention to one of the graphs in this blog post by Fraser Nelson on The Spectator's Coffee House blog on Friday.
Now, before I start I want to make it clear that I am a big fan of Fraser Nelson. He is an excellent columnist and is often able to cut through the crap and get to the real issues especially when it comes to figures and statistics. He has been forensic in his dissection of government figures and long may he continue to do this sort of important work.
Unfortunately his high standards seem to have eluded him a little in one of the graphs in the post referred to. I have reproduced the relevant section here:
Look at the number of jobs in the private sector and split it down by immigration status:So foreign-born workers account for all of the net job creation since 1997.
Now I am not arguing with the figures or his conclusion that foreign-born workers account for all of the net job creation since 1997. I am sure Fraser and the ONS have been rigorous about these and I will take it as read that this is correct. What I am arguing with (and what Matt pointed out to me) is the presentation of these figures. Fraser has the two lines superimposed on top of each other which invites direct comparison but he uses different starting points for the scales on each one.
The scale for the UK born workers runs from 17.8 million to 19.4 million on the left hand side and the scale for the foreign born workers runs from 1.4 to 3 million on the right hand side. I can see what he is trying to do (contrast the relative changes) but I think that this choice of scales would give someone who only glanced at this chart and didn't look closely enough to notice the disparity in scales the impression that the foreign-born figures have actually surpassed the UK-born figures as the UK-born figures have dropped off vertiginously at the end of last year.
This seems potentially very misleading to me and unneccesary. Fraser has a good enough argument without resorting to visual distortions like this.
I have tried to come up with a fairer way to represent this data. Of course I do not have the source data but I printed out the chart and by pinpointing the plot points on it I have been able to reverse engineer an approximation of this data. I have then produced my own versions of it.
Firstly, in order to demonstrate that I am using approximately the same data as Fraser, here is the data presented in a similar way to how he did it:
Secondly I adjusted the scales so that they are both the same running from 0 million to 20 million. This is now what the updated chart looks like.
This gives quite a different impression. The relative sizes of the different types of labour force are much clearer. This is fairer but of course you cannot see the changes in the data so easily this way so if I had been doing Fraser's post I would have also included two more charts with his original scales but with each data set on separate charts which would have made it clearer that they were different scales. They would then clearly be "explosions" of sections of the final chart above. This could even be represented by circling the data sets and pointing an arrow from them to the two sub-charts.
Putting them on the same one was destined to cause confusion in my view. His point is strong enough without this sort of potentially misleading representation.