How to measure what farms produce

How should we measure what farms produce? The answer drives some pretty important trends. For the past 60 years and more, the key metric has been yield – tonnes per hectare or equivalent. And it has resulted in extraordinary improvements in productivity, at least as measured by yield, and at least for some crops. Over the past 60 years, the productivity of the three major cereals – wheat, rice and maize – has gone up 3.2 times, more than keeping up with the 2.3-times increase in population. And ...