What supply means
Supply is the quantity of a good or service that producers are willing and able to sell at each possible price over a period of time. Higher prices usually make selling more profitable, so producers offer more for sale.
Key idea
The law of supply: as the price of a good rises, the quantity supplied rises, other things equal. So the supply curve slopes upward from left to right.
Movements along the curve
A change in the price of the good itself causes a movement along the supply curve. A rise in price causes an extension (more supplied); a fall in price causes a contraction (less supplied).
Example
When the market price of oranges rises, farmers offer more oranges for sale. This extension in supply is a movement up along the same supply curve.
Shifts in supply
A change in a factor other than price shifts the whole curve. Supply rises (shifts right) with lower costs of production, improved technology, better weather for crops, lower taxes or a subsidy. Higher costs or new taxes shift supply left.
Remember
- Price change → movement along the curve.
- Non-price change → shift of the whole curve.
- Lower production costs increase supply.