Module 3: Supply and Demand
What is Supply?
What you’ll learn to do: explain the determinants of supplySo far you've learned about the role of demand in economics—which is the consumer side of the story. In this section, you'll learn about the producer side of economics to see what factors impact the amount of goods supplied in a market. For example, suppose the global price of petroleum falls significantly. What do you think will happen to the supply of gasoline? How are supply and price connected? In this section you'll examine the law of supply and see why this counterpart to "demand" is also essential to understanding economics.
- Explain supply and the law of supply
- Identify and explain a supply curve
- Create and interpret a supply curve using a data set
Supply of Goods and ServicesWhen economists talk about supply, they mean the amount of some good or service a producer is willing to supply at each price. Price is what the producer receives for selling one unit of a good or service. A rise in price almost always leads to an increase in the quantity supplied of that good or service, while a fall in price will decrease the quantity supplied. When the price of gasoline rises, for example, it encourages profit-seeking firms to take several actions: expand exploration for oil reserves; drill for more oil; invest in more pipelines and oil tankers to bring the oil to plants where it can be refined into gasoline; build new oil refineries; purchase additional pipelines and trucks to ship the gasoline to gas stations; and open more gas stations or keep existing gas stations open longer hours. Economists call this positive relationship between price and quantity supplied—that a higher price leads to a higher quantity supplied and a lower price leads to a lower quantity supplied—the law of supply. The law of supply, like the law of demand, assumes that all other variables that affect supply are held equal (ceteris paribus).
Watch ItThe supply curve shows how much that sellers will be willing to provide at different prices. Because suppliers want to make a profit, companies have an incentive to sell more oil if it sells at a higher price.
Is Supply the same as Quantity Supplied?In economic terminology, supply is not the same as quantity supplied. When economists refer to supply, they mean the relationship between a range of prices and the quantities supplied at those prices, a relationship that can be illustrated with a supply curve or a supply schedule. When economists refer to quantity supplied, they mean only a certain point on the supply curve, or one quantity on the supply schedule. In short, supply refers to the curve, and quantity supplied refers to the (specific) point on the curve.
|Price and Supply of Gasoline
|Price (per gallon)
|Quantity Supplied (millions of gallons)
The shape of supply curves will vary somewhat according to the product: steeper, flatter, straighter, or curved. Nearly all supply curves, however, share a basic similarity: They slope up from left to right and illustrate the law of supply. As the price rises, say, from $1.00 per gallon to $2.20 per gallon, the quantity supplied increases from 500 gallons to 720 gallons. Conversely, as the price falls, the quantity supplied decreases.
Watch ItTo review the concepts of supply, watch this summary video from Dr. McGlasson:
glossarylaw of supply:
the common relationship that a higher price leads to a higher quantity supplied of a certain good or service and a lower price leads to a higher quantity supplied, while all other variables are held constantquantity supplied: the total number of units of a good or service producers are willing to supply at a given pricesupply: the relationship between the price of a certain good or service and the quantity of that good or service producers are willing to offer for sale supply curve: a graphic representation of the relationship between price and quantity supplied of a certain good or service, with price on the vertical axis and quantity on the horizontal axis supply schedule: a table that shows the quantity demanded for a certain good or service at a range of prices