Stock control Materials, once produced, are used up as they are given to students, lost, or wear out. It is possible to order quantities large enough to last for several years. This has benefits in that a long production run gives much cheaper unit costs than a short one. On the other hand large stocks mean that alterations are much more difficult and costly to make, however necessary they may be. Good anticipation of demand and of probable alterations can make very large differences to the overall cost.
Stocks have to be stored.
The benefits gained from the lower unit costs of long production runs have to be set against the cost of warehousing.