Well, that's because it's often not the case. Take the two cases: * Engines get more efficient (fewer litres per kilometre traveled). Does the total amount of

Well, that's because it's often not the case. Take the two cases: * Engines get more efficient (fewer litres per kilometre traveled). Does the total amount of petrol consumed go down or up? * Flushes get more efficient (less water / successful flush). Does the total amount of water consumed go down or up? Both of these have a more efficient use of a consumable quantity. Often, however, more efficient engines lead to more traveling and larger vehicles whereas more efficient flushing leads to reduced total water consumption usually. The fact that gains from efficiency can be outraced by the induced demand can be seemingly paradoxical. And "seemingly paradoxical" is the only thing that makes anything labelled "Paradox" interesting.