Agreed, it isn't clear to me what a 'good' conversion would be though. I suppose you could compare to an average wage or something, but then that doesn't captur

Agreed, it isn't clear to me what a 'good' conversion would be though. I suppose you could compare to an average wage or something, but then that doesn't capture subsistence farmers, or that there wasn't really a middle class then, or that on some measures a poor person today, is better off than a king from the 18th century. On top of that, the nature of the thing we are measuring has changed. Today it's a fruit, 250 years ago it's seeds and root were medicinal. All that said I'm struggling to work out where you got the billion £ figure from, or the 40x increase. The first 2 tables seem to suggest growth on the order of 100-150 fold, which would suggest £100 millions, rather than a billion, or am I misunderstanding something?