As price drops buyers increase the quantity demanded in part because additional buyers with lower reservation prices will now be interested in an exchange. Because buyers cannot buy as many goods as they want, there is a shortage of goods at that market price. During the next time period they will increase production and, because unit costs will be higher, will raise the price. As long as a shortage exists, there is pressure on sellers to push prices upward. As price rises, buyers decrease the quantity demanded in part because some buyers have a reservation price that becomes exceeded by a rising market price.
Buyers too are interested in gaining the most buyer's surplus as possible.
They will buy more or less as prices fall or rise because no surplus is enjoyed until a purchas is made. Although no one is directing these exchanges, a price is eventually reached where the quantity offered for sale is equal to the quantity purchased. We can use the mathemagical form of the demand and supply equations to calcuate the equilibrium price and quantity. 1999-2000 FTSS .