Partial measures, used in isolation,
can be misleading. A decline in the productivity of one input may be necessary
to increase the productivity of another. Such a trade-off is desirable if overall costs
decline, but the effect would be missed by using either partial measure. For example,
changing a process so that direct laborers take less time to assemble a product may
increase scrap and waste while leaving total output unchanged. Labor productivity
has increased, but productive use of materials has declined. If the increase in the
cost of waste and scrap outweighs the savings of the decreased labor, overall productivity
has declined.