Chapter 2.4.3: Equilibrium Levels of Real National Output
Welcome to one of the most important chapters in Macroeconomics! In this topic, we bring together everything you have learned about Aggregate Demand (\(\text{AD}\)) and Aggregate Supply (\(\text{AS}\)). Think of this chapter as the ultimate meeting place where buyers and sellers across the entire economy interact to determine two crucial things: total national production (Real GDP) and the general Price Level.
Don't worry if this seems tricky at first! Once you master the standard diagram setup and understand how the curves shift, you will be able to analyse almost any macroeconomic event with confidence.
---1. What is Equilibrium Real National Output?
Equilibrium real national output occurs at the point where total planned expenditure in the economy equals total planned output. In formula terms, this is where:
\(\text{AD} = \text{AS}\)
At this specific point, there is no unintended buildup or run-down of business inventories (stock), meaning there is no internal pressure for the general price level or real output to change.
An Everyday Analogy
Imagine a bakery for an entire country. If the bakers produce exactly 1,000 loaves of bread a day, and the citizens want to buy exactly 1,000 loaves at the going price, the bakery sells everything with zero waste and no disappointed customers. The market rests in balance. That balance, scaled up to all goods and services across the whole nation, is macroeconomic equilibrium.
Key Takeaway: Macroeconomic equilibrium is the level of real output where aggregate demand equals aggregate supply (\(\text{AD} = \text{AS}\)), setting the general price level and total output for the entire economy.
---2. The Essential Edexcel Diagram Rules
Diagram accuracy is vital in Edexcel Economics A. Examiners frequently note that students lose simple marks by mixing up microeconomic and macroeconomic labels.
Standard Labeling Conventions:
• Vertical Axis: Must be labelled Price Level (or \(P\) / Average Price Level). Never write just "Price" or "P (£)".
• Horizontal Axis: Must be labelled Real National Output, Real GDP, or \(Y\). Never write just "Quantity" or "Q".
• Equilibrium Coordinates: Always mark the equilibrium intersection clearly on the axes as \((PL_1, Y_1)\) or \((P_1, Y_1)\).
Quick Memory Trick: "PL-Y"
Remember the word "PLY": Price Level on the vertical axis, and \(Y\) (Real National Output) on the horizontal axis.
---3. Short-Run Macroeconomic Equilibrium and Output Gaps
Short-run equilibrium occurs at the intersection of Aggregate Demand (\(\text{AD}\)) and Short-Run Aggregate Supply (\(\text{SRAS}\)).
In the short run, the economy does not always produce at its maximum sustainable capacity. The equilibrium output level (\(Y_1\)) can sit below, at, or temporarily above the full-employment level of output (\(Y_f\)):
• Negative Output Gap (Recessionary Gap): Occurs when equilibrium real output (\(Y_1\)) is below the full employment level (\(Y_f\)), meaning \(Y_1 < Y_f\). In this situation, the economy has spare capacity, factories are idle, and there is cyclical unemployment.
• Positive Output Gap (Inflationary Gap): Occurs when equilibrium real output (\(Y_1\)) temporarily exceeds sustainable full employment capacity (\(Y_f\)), meaning \(Y_1 > Y_f\). This happens when firms push resources past normal limits using unsustainable overtime and extra shifts, creating upward pressure on costs and prices.
4. Long-Run Macroeconomic Equilibrium Models
Economists have different views on what happens to equilibrium in the long run. Edexcel requires you to understand and compare two major perspectives: the Classical (Monetarist) view and the Keynesian view.
A. The Classical / Monetarist View (Vertical LRAS)
Classical economists believe that markets naturally self-correct through wage and price flexibility.
• The LRAS Curve: In this model, Long-Run Aggregate Supply (\(\text{LRAS}\)) is a vertical straight line at the full employment level of real output (\(Y_f\)).
• Long-Run Equilibrium: Occurs where \(\text{AD} = \text{SRAS} = \text{LRAS}\).
• Adjustment Process: If \(\text{AD}\) increases, output may rise temporarily in the short run. However, workers and resource suppliers eventually demand higher wages and prices due to shortages. This raises production costs, shifting \(\text{SRAS}\) to the left until real output returns strictly to \(Y_f\). In the long run, shifts in \(\text{AD}\) affect only the price level, not real output.
B. The Keynesian View (Curved / Reverse-L LRAS)
Keynesian economists argue that wages and prices can be "sticky downwards" (inflexible), meaning an economy can remain stuck in a slump without automatically bouncing back to full employment.
The Keynesian \(\text{LRAS}\) curve has three distinct phases:
1. Spare Capacity Phase (Horizontal / Elastic): High unemployment and plenty of unused factory capacity. An increase in \(\text{AD}\) boosts real output (\(Y\)) without causing inflation because spare resources can be hired without raising wages or costs.
2. Bottleneck Phase (Upward Sloping): As output expands closer to capacity, shortages of specific skilled workers or raw materials emerge. An increase in \(\text{AD}\) leads to increases in both real national output and the price level.
3. Full Capacity Phase (Vertical / Inelastic): The economy hits its physical production boundary (\(Y_f\)). Any further increase in \(\text{AD}\) cannot increase real output and results purely in demand-pull inflation.
Did you know? The major policy takeaway of the Keynesian model is that an economy can settle at an equilibrium below full employment in the long run if there is a persistent deficiency of aggregate demand.
---5. Comparative Static Analysis: Shifts in Equilibrium
When an economic event causes \(\text{AD}\), \(\text{SRAS}\), or \(\text{LRAS}\) to shift, the old equilibrium breaks down and a new equilibrium price level and output level are established.
1. Shifts in Aggregate Demand (\(\text{AD}\))
Recall that \(\text{AD} = C + I + G + (X - M)\).
• Rightward Shift in \(\text{AD}\) (e.g., lower interest rates, fiscal stimulus, higher exports):
Increases equilibrium real national output (\(Y_1 \to Y_2\)) and increases the equilibrium price level (\(P_1 \to P_2\)), causing demand-pull inflation.
Exam Note: An initial autonomous injection can lead to an even larger final increase in equilibrium output due to the multiplier effect.
• Leftward Shift in \(\text{AD}\) (e.g., higher taxes, monetary tightening, falling consumer confidence):
Decreases equilibrium real national output (\(Y_1 \to Y_2\)) and places downward pressure on the price level.
2. Shifts in Short-Run Aggregate Supply (\(\text{SRAS}\))
\(\text{SRAS}\) is driven by the costs of production across the economy (e.g., wages, raw material prices, global oil prices, business taxes, exchange rates affecting imported components).
• Rightward Shift in \(\text{SRAS}\) (Falling production costs):
Increases equilibrium real national output (\(Y_1 \to Y_2\)) and lowers the price level (\(P_1 \to P_2\)).
• Leftward Shift in \(\text{SRAS}\) (Supply shock / cost-push):
Decreases equilibrium real national output (\(Y_1 \to Y_2\)) and raises the price level (\(P_1 \to P_2\)). This combination of falling output and rising prices is known as stagflation.
3. Shifts in Long-Run Aggregate Supply (\(\text{LRAS}\))
\(\text{LRAS}\) shifts when there are changes in the productive potential of the economy (e.g., improvements in education and skills, technological breakthroughs, increases in capital stock, improved enterprise).
• Rightward Shift in \(\text{LRAS}\):
Expands the maximum sustainable capacity of the nation (\(Y_{f1} \to Y_{f2}\)), increases equilibrium real output, and exerts downward pressure on the general price level.
6. Summary Comparison of Equilibrium Shifts
Use this quick reference to check the direction of shifts on the macroeconomic diagram:
• \(\text{AD}\) shifts Right (\(\uparrow\)): Price Level \(\uparrow\) | Real Output \(\uparrow\)
• \(\text{AD}\) shifts Left (\(\downarrow\)): Price Level \(\downarrow\) | Real Output \(\downarrow\)
• \(\text{SRAS}\) shifts Right (\(\uparrow\)): Price Level \(\downarrow\) | Real Output \(\uparrow\)
• \(\text{SRAS}\) shifts Left (\(\downarrow\)): Price Level \(\uparrow\) | Real Output \(\downarrow\) (Stagflation)
• \(\text{LRAS}\) shifts Right (\(\uparrow\)): Price Level \(\downarrow\) | Productive Capacity / Output \(\uparrow\)
7. Common Pitfalls to Avoid in the Exam
• Micro vs. Macro Labels: Always label the axes Price Level and Real National Output (or Real GDP / \(Y\)). Do not use \(P\) and \(Q\).
• Movements vs. Shifts: A change in the price level causes a movement along the curve (an extension or contraction). A change in any underlying determinant (like consumer confidence or oil prices) causes a shift of the entire curve.
• Mixing Up Classical and Keynesian Views: If you draw a vertical Classical \(\text{LRAS}\) curve, remember that shifts in \(\text{AD}\) do not change long-run real output. If you want to show persistent spare capacity in the long run, draw the curved Keynesian \(\text{LRAS}\) curve.
• Misinterpreting Stagflation: If an exam question asks about cost-push inflation or oil price spikes, shift the \(\text{SRAS}\) curve to the left, not the \(\text{AD}\) curve.
Final Tip: When answering essay or data response questions in Paper 2 or Paper 3, always explain the step-by-step transmission mechanism: start with the initial shock, identify which curve shifts and why, draw the new equilibrium coordinates \((P_2, Y_2)\), and conclude with the final effect on real output and the price level!