Stagflation is the combination of high inflation and high unemployment (with stagnant output) happening at the same time, usually caused by a negative supply shock. In the AP Macro Phillips curve model, it shows up as a rightward shift of the short-run Phillips curve.
Stagflation is the worst of both worlds. Inflation is high AND unemployment is high at the same time, while output stagnates or shrinks. That combination is weird, because the short-run Phillips curve (SRPC) says inflation and unemployment normally trade off against each other. When one goes up, the other goes down. Stagflation breaks that pattern.
Here's why it happens. The trade-off only holds for demand shocks, which move the economy along the SRPC (EK MOD-3.B.1). A negative supply shock, like a sudden spike in oil prices, raises production costs across the whole economy. Aggregate supply shifts left, so the price level rises and output falls together. In the Phillips curve model, that's a rightward shift of the entire SRPC (EK MOD-3.B.2). Now every point on the curve has both more inflation and more unemployment. The classic real-world example is the 1970s oil shocks, which is also the episode that convinced economists the long-run Phillips curve is vertical.
Stagflation lives in Topic 5.2 (The Phillips Curve) in Unit 5, and it's the scenario that makes learning objectives 5.2.B and 5.2.C come alive. You need to explain, with graphs, that supply shocks shift the SRPC while demand shocks move you along it, and stagflation is the test of whether you actually get that distinction. It also matters because it's the historical evidence behind the long-run Phillips curve (EK MOD-3.A.3). If there were a permanent inflation-unemployment trade-off, the 1970s shouldn't have been possible. Stagflation also connects back to Unit 2, since you can't even describe it without the vocabulary from Topic 2.4 (inflation, the inflation rate, CPI) and the unemployment rate from the business cycle topics. Finally, it's the great policy dilemma. Contractionary policy fights the inflation but worsens unemployment, and expansionary policy does the reverse, so there's no single demand-side fix.
Keep studying AP Macroeconomics Unit 2
Short-Run Phillips Curve (Unit 5)
Stagflation is what a rightward SRPC shift looks like in real life. A negative supply shock means every level of unemployment now comes with more inflation, so the old trade-off menu gets strictly worse.
Aggregate Supply (Units 3 and 5)
The AD-AS version of stagflation is a leftward shift of short-run aggregate supply. Price level up, real GDP down. The Phillips curve graph and the AD-AS graph are two pictures of the same supply shock, and the exam expects you to translate between them.
Inflation and the CPI (Unit 2)
The 'flation' half of stagflation is measured with a price index like the CPI (Topic 2.4). You can't identify stagflation in data without computing an inflation rate from CPI or the GDP deflator and pairing it with the unemployment rate.
Inflation Expectations (Unit 5)
If people expect the supply-shock inflation to stick around, expected inflation rises and the SRPC stays shifted right. That's how a temporary shock can turn into persistent stagflation, and why central banks care so much about anchoring expectations.
Stagflation shows up mostly in Unit 5 multiple-choice questions about the Phillips curve. Typical stems ask what happens when an economy at the natural rate of unemployment gets hit by a negative supply shock (answer: the SRPC shifts right, and inflation and unemployment both rise), or which economic phenomenon supports the existence of a vertical long-run Phillips curve (answer: the stagflation of the 1970s, when high inflation and high unemployment coexisted). The trap answers always involve confusing a movement along the SRPC with a shift of it. On FRQs, stagflation is usually tested without the word itself. You'll be told 'oil prices rise sharply' and asked to draw the AD-AS or Phillips curve graph, label the new equilibrium, and explain what happens to the price level, real output, and unemployment. Then comes the policy follow-up, where you explain why expansionary or contractionary policy fixes one problem while making the other worse.
Demand-pull inflation comes from a positive demand shock. Inflation rises while unemployment falls, which is a movement up and to the left ALONG the SRPC. Stagflation comes from a negative supply shock. Inflation rises while unemployment also rises, which means the whole SRPC has shifted right. Quick test: if inflation and unemployment move in opposite directions, think demand shock. If they move in the same direction (both up), think supply shock and stagflation.
Stagflation means high inflation and high unemployment at the same time, which violates the normal short-run trade-off shown by the Phillips curve.
It is caused by a negative supply shock, like an oil price spike, which shifts short-run aggregate supply left and the short-run Phillips curve right.
Demand shocks move the economy along the SRPC, but supply shocks shift the SRPC itself, and that distinction is exactly what stagflation questions test.
The 1970s stagflation is the empirical evidence that there is no long-run trade-off between inflation and unemployment, supporting a vertical long-run Phillips curve at the natural rate.
Stagflation creates a policy dilemma because fighting inflation with contractionary policy raises unemployment, while fighting unemployment with expansionary policy raises inflation.
You measure the two halves of stagflation with Unit 2 tools, using a price index like CPI for inflation and the unemployment rate for the labor market.
Stagflation is the combination of high inflation, high unemployment, and stagnant output occurring at the same time. In the AP Phillips curve model it appears as a rightward shift of the short-run Phillips curve caused by a negative supply shock.
No, but it proves the trade-off isn't permanent. The short-run Phillips curve still describes demand shocks fine; stagflation just shows the curve can shift when supply shocks hit. The 1970s episode is the standard evidence for a vertical long-run Phillips curve at the natural rate of unemployment.
In a typical demand-driven recession, unemployment rises but inflation falls, since you're moving down along the SRPC. In stagflation, unemployment rises AND inflation rises, because a supply shock shifted the SRPC right. Same direction of movement for both variables is the giveaway.
A negative supply shock. The classic example is a sharp rise in oil or energy prices that raises production costs economy-wide, shifting SRAS left in the AD-AS model and the SRPC right in the Phillips curve model.
Because monetary policy works through aggregate demand, and stagflation is a supply problem. Contractionary policy lowers inflation but pushes unemployment even higher; expansionary policy lowers unemployment but fuels more inflation. There's no single demand-side move that fixes both.