Does your finished product shrink or grow?

Do you know the key performance indicator which identifies the variation in tonnes of finished product leaving the mill, when compared with the tonnage of raw material which originally arrived? This is one vital question which far too many managers responsible for managing feed mills cannot answer accurately. When 100 tonnes raw materials arrive at the plant and 1% is lost in the process loss it means that only 99 tonnes leave. So why is it happening, how can it be identified and how can it be