AP Macroeconomics
Short Run and Long Run Equilibrium
Short-run equilibrium describes where the economy performs today relative to its potential (SRAS and AD). Long-run equilibrium is your sustainable capacity (LRAS). Economic growth shifts LRAS right; fluctuations are short-run performance relative to that capacity.
Macroeconomics is a Training Cycle, Not a Single Race. If you want to understand the difference between the Short Run and the Long Run, look at a marathon runner's training log.
1. The Daily Run: Short-Run Equilibrium (SRAS & AD)
Every day you lace up, you have a specific performance. This is the Short-Run.
The "Pumped" Run (Inflationary Gap)
One day you feel incredible. You have a tailwind, a perfect playlist, and you've had plenty of sleep. You run way faster than your average pace. You are "over-performing."
Macro Link: This is Aggregate Demand (AD) shifting right. You've pushed output () beyond your sustainable capacity ().
The "Sick" Run (Recessionary Gap)
Another day, you're exhausted or getting over a cold. You're sluggish, and your pace is terrible.
Macro Link: This is a decrease in AD or a supply shock. You are under-performing your potential.
2. The "Mean": Your Current Fitness (LRAS)
Your Current Fitness Level is the baseline—the sustainable output you can maintain. In the model, this is the Long-Run Aggregate Supply (LRAS): the level of real output the economy can produce at full employment.
In the short run, you can have a great day or a bad day relative to that baseline. In the long run, what matters is where that baseline sits. LRAS defines your capacity; short-run equilibrium is where AD and SRAS meet relative to that capacity.
3. The Training Program: Long-Run Growth
This is where the real magic happens. If you train consistently over six months, you aren't just having "good days"—you are changing your baseline.
Through better nutrition, more miles, and better shoes, your "8-minute mile" cruising speed becomes a "7-minute mile."
In the Economy
This is Economic Growth. You aren't just shifting the AD curve; you are shifting the LRAS curve to the right.
The Shifters
You've increased your Capital Stock (better gear/gym), your Human Capital (better running technique/knowledge), and your Technology (a more efficient training app).
The Dojo Distinction
- Short Run: Is about performance. Are you having a good day or a bad day relative to your current fitness?
- Long Run: Is about capacity. How has your training shifted the entire "mean" of what you are capable of doing?
AP Exam Tip
When the College Board asks about "Economic Growth," they are asking how the training went. When they ask about "Fluctuations," they are asking how today's run went.
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Check Your Understanding
Question 1 of 4
Assume an economy is initially in long-run equilibrium. The government then significantly increases its spending on infrastructure projects without changing taxes. In the short run, what is the most likely impact on the price level and real GDP?