ABSTRACT
It is quite wrong to overemphasize the change, from one positive quantity to another positive quantity, in the use of inputs as their prices change. Often enough the quantity will change from positive to zero, or vice versa. This is no doubt recognized in the most abstract arguments based, say, on production sets, but is given far too little attention in general. For electricity generation, for example, the wind turbine is vital to a windfarm but a complete irrelevance in a nuclear reactor, or a hydroelectric scheme. What might be called ‘on/off’ produced input use should be studied just as carefully as continuous changes in input use, as input prices change.
