AD-AS Model vs Stagflation
AD-AS Model and Stagflation are two Aggregate Demand & Supply concepts in AP Economics that students often mix up. The AD-AS model explains real output and the price level as the intersection of aggregate demand and aggregate supply. Stagflation is the simultaneous combination of stagnant growth, high unemployment, and high inflation. Here is how they compare side by side.
Aggregate demand slopes downward, short-run aggregate supply slopes upward, and long-run aggregate supply is vertical at full-employment output. Short-run equilibrium is where AD meets SRAS; long-run equilibrium is where all three curves intersect. It is the central model for analyzing recessions, inflation, and the effects of fiscal and monetary policy.
It is caused by a leftward shift of short-run aggregate supply, such as a sharp rise in oil prices (a negative supply shock). It is hard for policymakers because fixing unemployment and fixing inflation call for opposite policies. The 1970s U.S. economy is the classic example.
The AD-AS Model vs Stagflation: A Framework and the One Outcome It Cannot Cure From the Demand Side
| AD-AS Model | Stagflation | |
|---|---|---|
| What you do with it | Shift a curve and read the new equilibrium off the diagram | Recognize the outcome, then work backwards to the curve that moved |
| Curves in play | Two for a short-run question, three once the long run is involved | One, the short-run supply curve, moving left |
| Direction of the price level and real output | Depends entirely on which curve moved and which way | Price level up and real output down, always |
| How many single shifts produce it | Four are available, demand or supply, left or right | Only one of those four |
| What demand-side policy achieves | Whatever the question targets, since either curve can be addressed | Relief on one symptom and damage to the other |
| Gap that results | Recessionary, inflationary or none at all | Recessionary, while the price level is still climbing |
Run the diagram backwards and only one shift fits a rising price level with falling output
Most AD-AS work runs forwards: a shock arrives, you shift a curve, you read the result. Stagflation questions run backwards, handing you the result and asking which curve moved, and the reverse map has only four entries. A rightward demand shift raises the price level and raises output. A leftward demand shift lowers both. A rightward short-run supply shift lowers the price level and raises output. A leftward short-run supply shift raises the price level and lowers output. Only the last matches stagflation, so a prompt reporting both numbers has already given away its own answer. Take an illustrative economy where real GDP falls from 640 to 590 billion dollars while the price index rises from 100 to 108. No demand shift can produce that pairing, because demand shifts always move the two numbers the same way, so the mover is short-run aggregate supply. Having named the curve, name a cause from the supply determinant list: a jump in imported energy costs, a failed harvest, a negative productivity shock, a wage push. An answer blaming weak consumer spending contradicts the price index printed in its own question. Size the resulting gap at /calculate/recessionary-gap.
Every demand-side cure buys back one half of the problem by worsening the other
The dilemma is built into the geometry rather than into anybody's politics. Keep the illustrative economy at 590 billion dollars of real output, with potential output of 640 and a price index of 108. Expansionary fiscal or monetary policy shifts aggregate demand right, output recovers toward 640, unemployment falls, and the price index climbs past 108, so inflation gets worse. Contractionary policy shifts aggregate demand left, the price index eases back, and output drops below 590, so unemployment gets worse. Both policies work exactly as the model says they should. Neither repairs both symptoms, because any demand shift moves the price level and real output the same way while stagflation has them moving in opposite directions. The escape has to come from the supply side. Either the shock unwinds on its own as input costs come back down, which walks the short-run curve back right without policy, or measures that raise productivity and lower per-unit costs do the same job deliberately. That is also why stagflation appears as the short-run Phillips curve shifting outward rather than as a move along it, since unemployment and inflation are worsening together. Compare the tools at /macro/fiscal-policy.
Frequently asked questions
Which curve shifts in stagflation?
Short-run aggregate supply shifts left. That is the only single shift in the model producing a higher price level together with lower real output, since both demand shifts move the two numbers in the same direction and a rightward supply shift lowers the price level. Causes named on the determinant list include a spike in input costs, a negative productivity shock or a failed harvest.
Why can fiscal and monetary policy not fix stagflation?
Because both work by moving aggregate demand, and any demand shift changes the price level and real output in the same direction. Shifting demand right restores output but pushes the price level higher still. Shifting demand left cools the price level but drives output further below potential. Only a supply-side improvement, or the original shock unwinding, moves the two variables in opposite directions and repairs both at once.
How do you spot stagflation on an AD-AS diagram?
Look for the new equilibrium sitting up and to the left of the old one, meaning a higher price level paired with lower real GDP. Draw the vertical long-run curve as well, because the new equilibrium will sit to its left, and that distance is the recessionary gap making the combination awkward. Only a leftward short-run supply shift puts the intersection in that position.
Live AD/AS Model graph. Drag the curves, or open the full version.
Related comparisons
Get AP Econ exam tips in your inbox
Occasional emails with study tips, new interactive graphs, and exam-season reminders. Free, no spam.
No spam. Unsubscribe anytime. Read our privacy policy.
Keep track of what you have studied
A free EconLearn account adds progress tracking, your quiz history, and achievements. Studying here is free either way, and there is nothing to pay for as a student.
Create a free accountAlready have one? Sign in
Last updated