This document defines supply and the supply curve. It provides examples of individual supply curves for two wineries that make up the market supply curve. It explains that the quantity supplied at a given price point is where the supply curve is evaluated. The key determinants that can shift the supply curve are discussed, including the number of sellers, prices of resources, taxes/subsidies, technology, suppliers' expectations, prices of related/joint products. An increase in a determinant will shift the supply curve to the right and increase supply, while a decrease will shift it left and decrease supply.

1. Definition
Supply is the counterpart to demand. Demand is from the consumer's perspective while supply is
from the producer's. Supply in economics is defined as the producer's willingness and ability to
supply a given good at various price points, holding all else constant. An increase in price will
increase producer's revenues, thus they are willing to supply more; a decrease in price will
reduce revenues, therefore producers will supply less. The direct relationship between price and
quantity supplied of a good is known as the 'Law of Supply' and is typically represented by an
upward sloping line known as the supply curve.
Supply Curve
The supply curve shows the quantity supplied of a given product at varying price points, holding
all else constant. Each producer has his or her own supply curve for a given product, which can
vary from one producer to another depending on production costs and other variables. The
summation of the two individual supply curves will generate the market supply curve for that
product.
Consider two wineries in the Paso Robles region. Paso Winery may be willing to supply 20
bottles if the market price were $10/bottle but willing to supply 100 bottles if the price were
$50/bottle. Robles Winery may only be willing to supply 5 bottles if the price were $20/bottle
but 50 bottles if the price were $50/bottle. The summation of the two individual supply curves
creates a market supply curve with red wine ranging from $10/bottle up to $50/bottle. The two
individual supply curves differ in the prices the wineries are willing and able to supply red wine.
This may be due to vary input costs, such as the variety of grape being used, labor costs, or
technique of fermenting the grapes.
Quantity Supplied
Assume the supply of red wine in the Paso Robles area is depicted in the supply curve below.
The quantity supplied of red wine in the area is the amount of wine that would be supplied to
the market at a given price; in other words, evaluating the supply curve at a specific price point.
Assuming the market price for red wine is $30/bottle. At this price 60 bottles (point A) of red
wine would be supplied. If the price were to drop to $10/bottle, then only 20 bottles would be
supplied (point B). And at $50/bottle, 100 bottles of red wine would be supplied (point C). The

2. change in quantity supplied of red wine is a result of a change in market price. Moving from
point A to B or C is a movement along the supply curve. The actual supply curve did not change
shape, only the market price for red wine changed and thus the quantity supplied by the
producers changed.
Determinants of Supply :
Determinants of supply (also known as factors affecting supply) are the factors which influence
the quantity of a product or service supplied. We have already learned that price is a major factor
affecting the willingness and ability to supply. Here we will discuss the determinants of supply
other than price. These are the factors which are assumed to be constant in law of supply.
The price change of a product causes the price-quantity combination to move along the supply
curve. However when the other determinants change, the supply curve is shifted.
Following are the major determinants of supply other than price:
Number of Sellers
Greater the number of sellers, greater will be the quantity of a product or service supplied in a
market and vice versa. Thus increase in number of sellers will increase supply and shift the
supply curve rightwards whereas decrease in number of sellers will decrease the supply and shift
the supply curve leftwards. For example, when more firms enter an industry, the number of
sellers increases thus increasing the supply.
Prices of Resources
Increase in resource prices increases the production costs thus shrinking profits and vice versa.
Since profit is a major incentive for producers to supply goods and services, increase in profits
increases the supply and decrease in profits reduces the supply. In other words supply is
indirectly proportional to resource prices. Increase in resource prices reduces the supply and the
supply curve is shifted leftwards whereas decrease in resource prices increases the supply and the
supply curve is shifted rightwards.
Taxes and Subsidies
Taxes reduces profits, thereforeincrease in taxes reduce supply whereas decrease in taxes
increase supply. Subsidies reduce the burden of production costs on suppliers, thus increasing the
profits. Therefore increase in subsidies increase supply and decrease in subsidies decrease
supply.

3. Technology
Improvement in technology enables more efficient production of goods and services. Thus
reducing the production costs and increasing the profits. As a result supply is increased and
supply curve is shifted rightwards. Since technology in general rarely deteriorates, therefore it is
needless to say that deterioration of technology reduces supply.
Suppliers' Expectations
Change in expectations of suppliers about future price of a product or service may affect their
current supply. However, unlike other determinants of supply, the effect of suppliers'
expectations on supply is difficult to generalize. For example when farmers suspect the future
price of a crop to increase, they will withhold their agricultural produce to benefit from higher
price thus reducing the supply. In case of manufacturers, when they expect the future price to
increase, they will employ more resources to increase their output and this may increase current
supply as well.
Prices of Related Products
Firms which are able to manufacture related products (such as air conditioners and refrigerators)
will the shift their production to a product the price of which increases substantially related to
other related product(s) thus causing a reduction of supply of the products which were produced
before. For example a firm which produces cricket bats is usually able to manufacture hockey
sticks as well. When the price of hockey sticks increases, the firm will produce more hockey
sticks and less cricket bats. As a result, the supply of cricket bats will be reduced.
Prices of Joint Products
When two or more goods are produced in a joint process and the price of any of the product
increases, the supply of all the joint products will be increased and vice versa. For example,
increase in price of meat will increase the supply of leather.