That's a perfect example of "How to Lie With Statistics" you have found there, David. You are quite right. But how easily people are fooled, or fool themselves, by not appreciating that percentage share, change compared to a previous period and absolute numbers all give only a partial picture, and that picking the metric that best suits your case is so widespread.

The absolute figures, as you used, are the least misleading.

One of the things "Britannia Unchained" argues for is that people should do 'hard' degrees like mathematics and physical sciences, and of course a good understanding of mathematics would help avoid that confusion.

It seems a shame, then that the authors had these degrees themselves:

Dominic Raab - Law
Kwasi Kwarteng - classics and history
Priti Patel - Economics
Chris Skidmore - Modern History
Elizabeth Truss - Philosophy, Politics and Economics

(They did include Law as one of the hard degrees, but I didn't get as far as reading a rationale for that. And presumably the economics had some mathematical content, but it may not - there are some discursive forms)