We can easily illustrate macroeconomic inefficiency by examining the US food supply. We ask: the purpose of farmland is to do what with it?
Next, we ask, does the US have immense agricultural resources available?
So then, what do we do today?
First, we pay farmers not to grow X or Y. Then, we utilize farmland to grow crops, not to feed humans, but to feed cattle that would prefer grass and to create unnecessary biofuels. Let us also ship off some of the food that we do produce for humans to other nations that they may benefit from our production. The result? A reduced supply of food and inefficiency. Who benefits? Not the public.