Stagflation

In the AD–AS framework, movements along the aggregate demand curve produce inflation and growth together: stronger demand raises both the price level and real output. Stagflation breaks that co-movement because the disturbance originates on the supply side. A leftward shift of short-run aggregate supply, caused by higher input costs, a jump in energy or food prices, a fall in productivity, or a rise in wage demands not matched by output per hour, establishes a new short-run equilibrium at a higher price level and a lower level of real GDP.

The distinguishing signature is therefore the sign of the correlation between inflation and output. Demand-driven cycles produce positively correlated inflation and growth; supply-driven cycles produce negatively correlated inflation and growth. Because output falls below potential, the output gap turns negative and unemployment rises above its natural rate even while measured inflation accelerates.

Stagflation is analytically important because it removes the ordinary policy trade-off. Expansionary monetary or fiscal policy shifts aggregate demand right, which can restore output but pushes the price level higher still. Contractionary policy suppresses inflation but deepens the output loss and raises unemployment further. A central bank facing a supply shock must therefore choose which part of its mandate to sacrifice, at least temporarily.

The decision hinges on whether inflation expectations remain anchored. If households and firms treat the shock as transitory, the short-run aggregate supply curve eventually shifts back as input prices normalise and nominal wage growth moderates, and the economy returns toward potential output without policy action. If expectations become unanchored, workers bargain for compensating wage increases, firms pass those costs into prices, and a wage–price spiral entrenches inflation. That risk explains why credibility, and occasionally a deliberately induced recession, dominates central bank thinking in these episodes.

Practically, stagflation is diagnosed by combining indicators rather than any single series. Headline inflation exceeding core inflation points to energy and food shocks; producer price indices rising faster than consumer prices signal margin compression that has yet to reach the household. Simultaneously, industrial production, purchasing manager surveys and real retail sales weaken while unemployment claims climb. The misery index, the simple sum of the inflation and unemployment rates, is a crude but widely cited summary.

Asset markets respond distinctively. Nominal bonds suffer because yields rise on inflation while credit quality deteriorates with the cycle, so the traditional equity hedge fails. Equity valuations compress as discount rates rise and earnings estimates fall together. Commodities, commodity-linked equities, inflation-linked bonds and real assets tend to outperform, which is why strategists treat stagflation as a separate regime in scenario analysis rather than a variant of ordinary recession.

Exam questions rarely ask for a definition. They present a set of macro observations and ask you to identify the underlying shock, or they give a shock and ask for the direction of change in the price level, real output, unemployment and the output gap. Train yourself to draw the diagram quickly: shift SRAS left, mark the new intersection, read off the higher price level and lower real GDP, then infer that unemployment rises.

You should also be able to reason through the policy response, including the argument for policy restraint when a shock is judged temporary, and the argument for tightening when second-round effects into wages appear. Expect linkage questions to the Phillips curve, where a supply shock shifts the short-run curve outward so that any given unemployment rate is associated with higher inflation, and to portfolio implications, where the breakdown of the usual inflation–growth relationship changes which asset classes provide protection.