Welcome to the World of Aggregate Supply!
In our previous studies, we looked at Aggregate Demand (AD)—the total spending in an economy. Now, it’s time to look at the other side of the coin: Aggregate Supply (AS).
Think of AS as the "production" side of the economy. We are going to focus specifically on the Short-run AS (SRAS). Understanding this is vital because it helps us see how changes in costs, like energy prices or taxes, can affect the entire country's output and price levels. Don’t worry if this seems a bit abstract at first; we’ll break it down using examples you see every day!
1. What exactly is Aggregate Supply?
Aggregate Supply (AS) is the total volume of goods and services produced within an economy at a given price level over a specific time period.
In the short run, we assume that at least one factor of production (like the size of a factory or the technology available) is fixed. Most importantly, we assume that the costs of production (like wages) haven't had time to fully adjust to changes in the economy yet.
The Shape of the SRAS Curve
The SRAS curve slopes upwards from left to right. This shows a positive relationship between the price level and the amount of output firms are willing to supply.
Why does it slope upwards? Imagine you own a bakery. If the general price level of bread rises, but your costs (like flour and rent) stay the same for now, your profit margin increases! Naturally, you’ll want to bake and sell as much bread as possible to make the most of those high prices.
Quick Review:
- SRAS = Total production in the economy.
- Slope = Upwards (as prices go up, firms want to produce more).
- Short Run = A period where costs like wages are "sticky" (they don't change instantly).
2. Movements vs. Shifts in SRAS
It is very important to distinguish between a movement along the curve and a shift of the entire curve. This is a common area where students lose marks, so let's get it right!
Movements Along the Curve
A movement along the SRAS curve happens only when the Price Level changes.
- If the price level rises, there is an expansion of supply.
- If the price level falls, there is a contraction of supply.
Shifts of the Curve
A shift happens when the costs of production for firms change. If it becomes more expensive to produce goods, the SRAS curve shifts to the left (less is supplied at every price). If it becomes cheaper, it shifts to the right.
Key Takeaway:
- Price Level changes = Movement along the line.
- Cost changes = The whole line moves (Shift).
3. Factors Influencing Short-run AS (The "Shifters")
What makes the whole SRAS curve move? According to your syllabus, there are three main factors you need to know. A good way to remember these is the mnemonic "CET" (like the word 'set' but with a C): Costs, Exchange rates, and Taxes.
A. Changes in Costs of Raw Materials and Energy
Raw materials (like oil, gas, and electricity) are used by almost every business. If the price of oil goes up, it costs more to transport goods and run machinery.
Example: If the price of electricity doubles, a steel factory's costs skyrocket. They can’t afford to produce as much as before, so SRAS shifts left.
B. Changes in Exchange Rates
If the value of the British Pound (\( £ \)) falls (depreciates), it becomes more expensive to buy things from abroad. Since many UK firms import raw materials from other countries, their production costs will rise.
Step-by-step:
1. Pound value falls.
2. Cost of imported raw materials rises.
3. Firms' total production costs increase.
4. SRAS shifts left.
C. Changes in Tax Rates
We are specifically talking about indirect taxes (like VAT or Fuel Duty) and subsidies.
- Taxes: If the government increases the tax on petrol, it costs businesses more to deliver goods. This acts like an increase in production costs, shifting SRAS to the left.
- Subsidies: If the government gives a subsidy (financial help) to energy companies, their costs effectively fall, shifting SRAS to the right.
Did you know?
Oil is often called the "blood of the economy." Because it's used in plastic, heating, and transport, a spike in oil prices can cause the SRAS of almost every industry to shift left at the same time!
4. The Relationship Between SRAS and LRAS
While SRAS is about how much firms can produce right now based on their current costs, Long-run AS (LRAS) is about the total capacity of the economy when all costs have adjusted.
Think of it this way:
- SRAS is like how fast you can run today (you might be tired or have a cold).
- LRAS is your potential top speed if you were perfectly healthy and had the best training.
In the short run, an economy can actually produce more than its long-term limit (by making workers do lots of overtime), but this isn't sustainable because eventually, workers will demand higher wages, pushing costs up and shifting the SRAS back.
Key Takeaway:
The SRAS shows the relationship between prices and output when costs are temporary; the LRAS shows the economy's potential when everything is stable.
Summary Checklist
Before you move on, make sure you can answer these:
- Why is the SRAS curve upward sloping? (Hint: Profit margins!)
- What is the only thing that causes a movement along the SRAS curve? (Hint: Price Level!)
- What happens to the SRAS curve if the Pound gets stronger? (Hint: Imports get cheaper, so SRAS shifts right.)
- Can you name the "CET" factors that shift the curve?
Don't worry if you find the diagrams tricky at first. Just remember: if it's "bad news" for a firm's bank account (higher costs), the curve moves left. If it's "good news" (lower costs), it moves right!