Welcome to Price Elasticity of Supply!
In the last few chapters, we learned that when prices go up, businesses want to supply more. But here is the big question: how much more will they actually produce? Some businesses can double their output overnight, while others might take years to change a thing. This "responsiveness" is what we call Price Elasticity of Supply (PES).
Don't worry if this seems a bit technical at first—by the end of these notes, you'll be an expert on why some businesses are "stretchy" like a rubber band and others are "stiff" like a brick!
1. What is Price Elasticity of Supply (PES)?
Price Elasticity of Supply (PES) measures how much the quantity supplied of a product changes when its price changes.
Think of it as a "reaction test" for businesses:
- High Elasticity: The business reacts strongly to a price change.
- Low Elasticity: The business reacts weakly to a price change.
Elastic vs. Inelastic Supply
Price Elastic Supply: This happens when the percentage change in quantity supplied is greater than the percentage change in price. If the price goes up a little, the business increases production a lot!
Example: A taxi driver can easily work more hours if the fare prices increase.
Price Inelastic Supply: This happens when the percentage change in quantity supplied is less than the percentage change in price. Even if the price shoots up, the business can't increase supply by much.
Example: A farmer growing apples. If apple prices double today, the farmer can't grow new trees instantly; it takes years!
Key Takeaway: Elastic = Very responsive to price. Inelastic = Not very responsive to price.
2. How to Calculate PES
To find the PES, we use a simple formula. In your exam, you will usually be given the percentage changes, or you’ll need to work them out first.
The formula is:
\( \text{PES} = \frac{\% \text{ change in quantity supplied}}{\% \text{ change in price}} \)
Step-by-Step Calculation:
1. Find the % change in Quantity Supplied.
2. Find the % change in Price.
3. Divide the Quantity % by the Price %.
Memory Aid: Always keep "Q" on top! Just remember the alphabet: Q comes before P. So, Quantity is the numerator (top), and Price is the denominator (bottom).
Interpreting the Result:
- If the answer is greater than 1, supply is elastic.
- If the answer is less than 1, supply is inelastic.
- If the answer is exactly 1, it is called Unit Elastic Supply.
Quick Review: If price rises by 10% and supply rises by 20%, \( \text{PES} = 20 / 10 = 2 \). Since 2 is bigger than 1, the supply is elastic.
3. Factors Affecting PES
Why are some goods more elastic than others? It usually comes down to how easy it is for a business to change its production levels.
A. Time Period
This is the most important factor!
- In the short run, supply is usually inelastic because firms find it hard to change their factory size or hire new specialized staff quickly.
- In the long run, supply becomes more elastic because firms have time to build new factories and expand.
B. Availability of Stock (Inventories)
If a firm has a huge warehouse full of finished goods (stock), supply is elastic. If the price goes up, they just ship the goods out immediately! If they have no stock (like fresh strawberries), supply is inelastic.
C. Spare Capacity
If a factory is only running at 50% capacity (its machines are sitting idle half the time), supply is elastic. They can easily turn the machines on to produce more if prices rise. If the factory is already running 24/7, supply is inelastic.
D. Ease of Switching Production
Can the business switch from making one product to another?
Example: A printing company can easily switch from printing magazines to printing brochures if the price of brochures rises. This makes their supply elastic.
Key Takeaway: If it's easy and fast to produce more, supply is elastic. If it's difficult or slow, supply is inelastic.
4. Why PES Matters to Producers and Consumers
For Producers (Businesses):
Producers want their supply to be as elastic as possible. Why? Because if the market price suddenly jumps, an elastic business can react quickly to produce more and capture higher profits. If their supply is inelastic, they might miss out on the "gold rush" because they can't make the goods fast enough.
For Consumers:
PES affects how much prices change when demand shifts.
- If supply is inelastic and everyone suddenly wants the product (demand increases), the price will skyrocket because firms can't produce more fast enough.
- If supply is elastic, the price won't rise as much because firms will simply increase supply to meet the new demand.
Did you know? This is why tickets for a one-off concert (inelastic supply) are so expensive if demand is high, but the price of a popular chocolate bar (elastic supply) stays relatively stable even when more people want them.
5. Summary Quick-Check
Common Mistakes to Avoid:
- Mixing up Demand and Supply: Ensure you are looking at the producer's reaction (Supply), not the consumer's (Demand).
- Putting Price on top: Remember the "Q before P" rule! Quantity % change always goes on top of the formula.
- Forgetting Time: Always remember that supply is almost always more elastic in the long run than the short run.
Quick Review Box:
- PES Formula: \( \% \Delta \text{QS} / \% \Delta \text{P} \)
- PES > 1: Elastic (Stretchy/Responsive).
- PES < 1: Inelastic (Stiff/Unresponsive).
- Main Factor: Ease and speed of production.
Don't worry if this feels like a lot to take in! Just remember: PES is simply a way of measuring how "helpful" a business can be when prices change. If they can help by making more goods quickly, they are elastic!