Market prices are the foundation of civilization. They are the signal that tells producers how much of any one thing to produce. They tell consumers how much to consume or whether to consume a product at all. The reason retailers don't normally throw away 80 percent of their stock is because market prices tell them how much to have on hand at any one time to meet current demand.

When they miscalculate and buy a little too much, they still don't typically waste their stock. They put it on sale and meet the demand at a lower price.

To the extent the market is allowed to set prices, producers generally produce what consumers want to buy in the quantities they want to buy. When all supply is consumed and large amounts of consumers are not left with unmet demand, it is referred to as the market "clearing."