Price Elasticity of Supply
What is Price Elasticity of Supply?
Price elasticity of supply measures how responsive the quantity supplied is to a change in price.
It is calculated as the percentage change in quantity supplied divided by the percentage change in price. Supply is considered elastic if the ratio is greater than 1, meaning the quantity supplied changes more than the price. Supply is inelastic if the ratio is less than 1.
Price Elasticity of Supply: a worked example
A coffee grower is paid $8 per pound and ships 40,000 pounds. The price rises to $10 and shipments rise to 46,000 pounds over the season. The percentage change in quantity supplied is 6,000 ÷ 40,000 = 15 percent. The percentage change in price is $2 ÷ $8 = 25 percent. Price elasticity of supply is 15 ÷ 25 = 0.6, so supply is inelastic: quantity responded proportionally less than price. The midpoint method reaches the same verdict, since 6,000 ÷ 43,000 = 13.95 percent divided by $2 ÷ $9 = 22.2 percent gives 0.63. Give the grower several seasons to plant and mature more trees and that same $2 price rise could lift output to 70,000 pounds, a 75 percent gain, so elasticity becomes 75 ÷ 25 = 3.0 and supply is now elastic.
The mistake students make with price elasticity of supply
The habit that ruins the answer is dividing raw units instead of percentages: 6,000 extra pounds ÷ a $2 price rise gives 3,000. That figure is 3,000 pounds per dollar, a units bound rate rather than an elasticity, and restating the same harvest in tons turns it into 3 ÷ 2 = 1.5 without anything real having changed. Convert each change into a percentage of its own starting value first, then divide, and the answer stops depending on the measuring stick. The second slip is treating elasticity as a fixed trait of the crop. This grower is far more responsive across several seasons, when new trees can be planted, than within one harvest.
Price Elasticity of Supply questions
Is price elasticity of supply positive or negative?
Price elasticity of supply comes out positive, because the law of supply makes price and quantity supplied move in the same direction. A higher price raises quantity supplied, so both percentage changes carry the same sign and the ratio lands above zero. Price elasticity of demand is the opposite case, negative by nature, which is why courses tell you to drop the sign there. No sign dropping is needed for supply, so a negative answer signals an arithmetic error worth rechecking.
What makes supply more elastic?
Supply becomes more elastic when producers can change output quickly and cheaply. Spare factory capacity, easily hired inputs, storable inventory, and resources that move readily between uses all raise the coefficient. Time matters most: over a single day output is nearly fixed, while over several years firms can build plants and new firms can enter. Goods with long production lags, such as tree crops or mined minerals, have very inelastic supply in the short run.
How do you tell if supply is elastic or inelastic?
Compare the coefficient with 1. A value above 1 means quantity supplied changed proportionally more than price, so supply is elastic. A value below 1 means quantity responded proportionally less, so supply is inelastic. A value of exactly 1 is unit elastic. On a graph, a flatter supply curve through a given point is the more elastic one, and any straight supply curve drawn through the origin is unit elastic no matter how steep it looks.
Formula / Example
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