A frost that cuts the coffee crop pushes the price up
Suppose the coffee crop in Brazil suffers a terrible frost. The supply curve of coffee shifts to the left and the price of coffee rises. Nobody has to decide that it should: at the old price buyers want more coffee than there now is, and the price climbs until the two match again.
1 of 3
Before the frostAt P1 buyers want Q1 and growers supply Q1.
The higher price decides who gets the coffee that is left
Some people continue to drink coffee and pay the higher price. Others switch to tea or soft drinks. No government commission is needed to decide which consumers will be allowed to drink what remains: the price shares the smaller crop out among the buyers who value it most.