The quantity demanded of a commodity depends on the expected price of the commodity in the future. Consumers who expect the price of a commodity to increase will decide to purchase that commodity sooner than later and vice versa applies.
EXAMPLE
The lack of new residential construction in a popular residential suburb will create a shortage of cottages within that suburb the next year. This will increase the price of existing cottages so that consumers will tend to purchase available cottages in the rising market as quickly as possible.
EXAMPLE
Because of an excess number of cottages in the course of construction, the price of cottages in a particular suburb is expected to decrease within the next year. Consumers will therefore, postpone purchasing until that time thus deflating the current market.