A topic in the Open Knowledge Graph — a free, open map of 15,290 topics and the order to learn them in.
Supply shocks (oil price spikes, crop failures, productivity declines) shift aggregate supply leftward, raising prices and reducing output simultaneously—stagflation. Unlike demand shocks, which produce a tradeoff between inflation and unemployment, supply shocks worsen both. Supply shocks are particularly difficult for policymakers: stimulating demand alleviates unemployment but worsens inflation, while restricting demand reduces inflation but increases unemployment.
Supply shocks are disruptions to the economy's productive capacity rather than to spending. From your study of aggregate supply, you know the short-run AS curve reflects the costs of production—when those costs rise suddenly (an oil price spike, a war disrupting supply chains, a poor harvest), firms can produce less at every price level. The AS curve shifts leftward, and the new intersection with the AD curve sits at a higher price level *and* lower real output simultaneously. This combination—inflation plus recession—is stagflation, and it is what made the 1970s oil crises so economically painful.
What makes stagflation uniquely difficult is the policy trap it creates. You already know that inflation arises when output exceeds potential (demand-pull) or costs rise (cost-push), and that unemployment rises when output falls below potential. Normally these problems appear separately: recession → stimulate demand; inflation → restrict demand. A supply shock destroys this separation. Both problems appear at once, and any policy response that addresses one aggravates the other.
Consider the policymaker's choices after an adverse supply shock. If they expand fiscal or monetary policy to fight the recession (moving along the new, higher-cost AS curve toward higher output), they accept even higher inflation—the AD curve shifts right, raising the price level further. If they tighten policy to fight inflation—restricting demand—they push output down further, deepening the recession. There is no clean medicine for stagflation within the standard demand-management toolkit. The only true cure is a positive supply shock that reverses the original disruption (e.g., energy prices falling back), or long-run supply-side policies that improve productivity.
Positive supply shocks work in reverse: a technological breakthrough, a fall in commodity prices, or increased labor force participation shifts AS rightward—lower prices and higher output simultaneously. These combine the benefits of both anti-inflation and anti-recession policies at once. Recognizing whether a shock is supply-side or demand-side is therefore the first analytical task in any macroeconomic diagnosis, because the policy response must be matched to the shock type.