a) An indicator for the output or value added generated per unit of "nature" (materials/energy/pollution) used.
b) A social action strategy which seeks to reduce the use of materials in the economy in order to reduce undesirable environmental impacts. Ever smaller quantities of materials have to produce a relatively higher degree of economic affluence. The general objective of eco-efficiency is to "get more from less" (this is known as qualitative growth).
Eurostat, "Economy-wide material flow accounts and derived indicators - A methodological guide", Office for official publications of the European Communities, Luxembourg, 2000