What it means
Imagine a bakery that makes loaves of bread. At a price of $2 a loaf it might bake only a small batch, because many of its costs are not covered, while at $5 a loaf it will happily run extra shifts.
Plot those choices on a chart, with price on the vertical axis and quantity on the horizontal axis, and you have a supply curve. The upward slope reflects rising costs.
Producing more usually means paying overtime, buying from less efficient suppliers or using older equipment, so each extra unit costs more to make. A seller will only supply those extra units if the price is high enough to cover the higher cost.
The curve describes the relationship between price and quantity supplied, holding everything else constant. When something else changes, such as the cost of raw materials, new technology or a tax on the product, the whole curve shifts.
Cheaper materials move the curve to the right, so more is supplied at every price, while a new tax moves it to the left. Economists measure how responsive supply is with the price elasticity of supply, which compares the percentage change in quantity with the percentage change in price.
If supply is elastic, producers can increase output easily when prices rise, as with a software product that costs little to copy. If it is inelastic, output is slow to respond, as with farmland or a power station that takes years to build.
For managers and finance teams, the supply curve helps in forecasting costs and planning purchases. A buyer of steel, for instance, can see that pushing demand higher may raise prices if suppliers are close to capacity.
Combined with the demand curve, it shows where the market price settles, which is where the quantity supplied equals the quantity demanded. The nuance is that real supply curves are rarely perfectly straight or smooth.
In the very short run, output may be fixed whatever the price, and in the long run new competitors can enter and change the shape. The textbook curve is a simplified guide, not a precise forecast.
In practice
Real-world examples.
Example
A coffee grower sees the global price rise by 30% and decides to plant extra land. Because new trees take years to produce a crop, the supply response is slow, which shows that coffee supply is inelastic in the short run.
Example
A software company sells subscriptions that cost almost nothing to add per customer. When prices rise it can serve many more customers quickly, so the supply curve is flat and very elastic.
Example
A building materials manufacturer is operating at full capacity. A rise in cement prices from $120 to $150 a tonne brings only a small increase in output, because the plant cannot produce more without new equipment.
Formula
Calculation
Linear supply curve: quantity supplied = a + b x price
Price elasticity of supply = percentage change in quantity supplied / percentage change in price
Suppose a bakery's supply is described by Q = 100 + 20 x P, where Q is loaves per day and P is the price in dollars. At a price of $5, Q = 100 + 20 x 5 = 200 loaves. At a price of $10, Q = 100 + 20 x 10 = 300 loaves. The price has risen by (10 - 5) / 5 = 100%, and the quantity has risen by (300 - 200) / 200 = 50%. The elasticity of supply is 50% / 100% = 0.5, so supply is relatively inelastic over this range.Case study
Seen in the real world.
Clearwater Pallets is an illustrative, fictional company that makes wooden shipping pallets. When demand from warehouses surged, its sales director wanted to accept every order at the current price of $12 a pallet.
The finance manager sketched the company's supply curve from cost data. Up to 50,000 pallets a month, the cost per pallet was about $9, but beyond that the company had to pay overtime and buy timber at higher prices, and the cost rose to $14 at 70,000 pallets.
Based on the curve, the company decided to accept extra orders only at a price of at least $15. In this illustrative case, it earned less volume but a higher margin, and avoided the loss that would have come from selling the most costly pallets for $12.
Watch out
Common mistakes.
- Confusing a movement along the curve, caused by a price change, with a shift of the whole curve, caused by factors such as costs or technology.
- Assuming the curve is the same in the short run and the long run, when producers have more flexibility with more time.
- Treating the supply curve as a record of what a firm sold, when it shows what producers would be willing to sell at each price.
Questions
People also ask.
Why does the supply curve slope upward?
Producing more normally costs more per unit, so sellers need a higher price to make the extra output worthwhile.
What shifts the supply curve?
Changes in input costs, technology, taxes, subsidies, the number of sellers and expectations about future prices can all shift it.
How does the supply curve relate to the demand curve?
Together they determine the market price, which is the point where the quantity suppliers offer equals the quantity buyers want.
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