In the Middle Ages the yield of wheat of an acre of land in England was fourfold, to-day it is ten to twenty fold, and in addition to that five times more land is cultivated.

• 英国小麦每英亩的产量，在中世纪时已比前增加到四倍，现在已增加到十倍至二十倍，此外耕地面积也已扩大到五倍以上。