Price controls
In the 4th century BC, Lactantius wrote that Diocletian "by various taxes he had made all things exceedingly expensive, attempted by a law to limit their prices. Then much blood [of merchants] was shed for trifles, men were afraid to offer anything for sale, and the scarcity became more excessive and grievous than ever. Until, in the end, the [price limit] law, after having proved destructive to many people, was from mere necessity abolished."  As with Diocletian's Edict on Maximum Prices, shortages lead to black markets where prices for the same good exceed those of an uncontrolled market. Furthermore, once controls are removed, prices will immediately increase, which can temporarily shock the economic system.