Welcome to the World of Price Elasticity of Supply (PES)!
Ever wondered why some businesses can suddenly produce thousands of extra products when prices go up, while others seem stuck with what they have? That is exactly what Price Elasticity of Supply (PES) is all about! In this chapter, we will explore how producers react to price changes. Think of it as measuring how "stretchy" or "flexible" a business is when it sees a chance to make more money.
By the end of these notes, you’ll be able to calculate PES, understand why some businesses are faster than others, and see how time plays a massive role in Economics.
1. Defining Price Elasticity of Supply (PES)
Price Elasticity of Supply (PES) measures the responsiveness of the quantity supplied of a good to a change in its price.
In simpler terms: If the price of a chocolate bar goes up by 10%, how much more chocolate will the factory try to make? If they can increase production by a lot (say 20%), their supply is elastic (stretchy). If they can only increase it by a tiny bit (say 2%), their supply is inelastic (stiff).
Key Takeaway: PES is all about the reaction of producers. High PES = Big reaction. Low PES = Small reaction.
2. The PES Formula and Calculation
To find the PES, we use a simple ratio. Don't worry if you aren't a math fan—it's just a bit of division!
The Formula:
\(\text{PES} = \frac{\% \Delta \text{ Quantity Supplied}}{\% \Delta \text{ Price}}\)
(Note: The symbol \(\Delta\) means "change in".)
How to calculate it step-by-step:
1. Find the percentage change in quantity supplied: \(\frac{\text{New Quantity} - \text{Old Quantity}}{\text{Old Quantity}} \times 100\)
2. Find the percentage change in price: \(\frac{\text{New Price} - \text{Old Price}}{\text{Old Price}} \times 100\)
3. Divide the result of step 1 by the result of step 2.
The Sign of the Coefficient
Unlike Price Elasticity of Demand (which is usually negative), the PES coefficient is always positive. This is because of the Law of Supply: as price goes up, firms want to supply more to earn more profit. They move in the same direction!
Memory Tip: Always put Quantity on top. Remember: "Q over P". If it helps, think of the Queen sitting on the Prince!
3. Understanding the PES Values
The number you get from your calculation tells a specific story about the business:
1. Elastic Supply (PES > 1): The percentage change in quantity is greater than the percentage change in price.
Example: Price rises 10%, supply rises 50%. This firm is very flexible!
2. Inelastic Supply (PES < 1): The percentage change in quantity is less than the percentage change in price.
Example: Price rises 10%, supply only rises 2%. This firm is struggling to make more.
3. Unitary Elasticity (PES = 1): The percentage change in price and quantity are exactly the same.
4. Perfectly Inelastic (PES = 0): No matter how much the price changes, the quantity supplied stays the same. The supply curve is vertical.
Analogy: A football stadium for a final match. Even if tickets cost $1,000,000, you can't add more seats overnight!
5. Perfectly Elastic (PES = \(\infty\)): At a specific price, supply is infinite, but if the price drops even a tiny bit, supply falls to zero. The supply curve is horizontal.
Quick Review:
Number > 1: Elastic (Reactive)
Number < 1: Inelastic (Unreactive)
Number = 0: Perfectly Inelastic (Fixed)
4. Factors Affecting PES
Why are some products more "stretchy" than others? Here are the main factors you need to know for your exam:
A. Time Period (The Most Important Factor!)
In the short run, at least one factor of production is fixed (like the size of the factory). It is hard to increase supply, so PES is usually inelastic.
In the long run, all factors are variable. You can build new factories and hire more staff, making PES elastic.
B. Availability of Stocks (Inventories)
If a firm has a huge warehouse full of finished goods, they can react instantly to a price rise by just shipping them out. This makes supply elastic. Perishable goods (like fresh milk) can't be stored easily, so their supply is more inelastic.
C. Spare Capacity
Is the factory running at 100% capacity? If the machines are already running 24/7, the firm can't produce more without a big investment (inelastic). If the machines are only running half the time, they can easily ramp up production (elastic).
D. Mobility of Factors of Production
Can workers and machines be easily switched from making one product to another? If a farmer can switch from growing wheat to growing barley very quickly, the supply of barley is elastic.
Memory Aid: Think of the word S.T.O.C.K.
Spare capacity
Time period
Obstacles to moving resources
Complexity of production
Keepable stocks (inventories)
5. Implications for Firms
Why should a business owner care about PES? It determines the speed and ease with which they can react to market changes.
Firms want their supply to be as elastic as possible. Why? Because if the price of their product suddenly sky-rockets due to a trend, an elastic firm can produce more quickly and capture all that extra profit. An inelastic firm will miss out because they can't make the goods fast enough.
Did you know? This is why many modern factories use "Flexible Manufacturing Systems." They want to be able to change what they are making in hours, not months, to keep their PES high!
Key Takeaway: High PES = Competitive Advantage. It means the firm is agile and ready to grab opportunities.
Common Mistakes to Avoid
1. Confusing PES with PED: PES is about producers (supply); PED is about consumers (demand). Always check which curve you are looking at!
2. Forgetting the Sign: Remember that PES is almost always positive. If you get a negative number, check your math—you might have accidentally used demand data.
3. Vertical vs. Horizontal: Remember that Inelastic starts with an "I", and a perfectly inelastic curve looks like a tall letter I (vertical). Perfectly Elastic looks like the horizontal bars of an E (if you tip it over!).
Final Summary Quick-Check
Definition: How much supply changes when price changes.
Formula: % change in Quantity / % change in Price.
Elastic: Result > 1 (Flexible production).
Inelastic: Result < 1 (Rigid production).
Main Driver: Time. The more time a firm has, the more elastic their supply becomes.