This is a troublesome concept when dealing with beans. In the United States, with conventional harvest systems, losses average 4 percentage of yield, ranging from 1 percentage to 12 percentage. It mostly happens during the combining operation, with about half of this loss attributed to header and half to threshing loss (26).
Where beans are grown on a small scale or for subsistence, losses are much higher. Only rough estimates can be made and they are unreliable. Losses may be zero when beans are harvested by pulling plants from small plots and transporting bundles immediately to the threshing place, as performed by women in Uganda as no pod shattering occurs. When pulled and heaped for field drying before threshing, pod shattering depends strongly on weather conditions, and if these are adverse, losses can be heavy (20 percentage-30 percentage).
See under 4.1 for storage losses to bruchids.