It didn't improve efficiency by much for a long time. In the end of the western roman empire there were epidemics and the population was greatly reduced. Befor

It didn't improve efficiency by much for a long time. In the end of the western roman empire there were epidemics and the population was greatly reduced. Before the plague, great amounts of land were used for crops, even if the yield was low. After the plague, they started to have cows or sheeps instead, since they needed less food. Source: avid listener of Alessandro Barbero's lectures :)