--- title: "Supply Shocks — AP Macro Definition & AD-AS Exam Guide" description: "A supply shock is a sudden, unexpected shift in SRAS that moves output and the price level in opposite directions. Key to stagflation and cost-push inflation on the AP exam." canonical: "https://fiveable.me/ap-macro/key-terms/supply-shocks" type: "key-term" subject: "AP Macroeconomics" --- # Supply Shocks — AP Macro Definition & AD-AS Exam Guide ## Definition In AP Macro, a supply shock is an unexpected event that suddenly shifts short-run aggregate supply (SRAS); a negative shock raises the price level while output and employment fall (stagflation), and a positive shock lowers the price level while output and employment rise. ## What It Is A [supply](/ap-macro/unit-1/supply/study-guide/auVQK1N9VWZQ0TOeix3K "fv-autolink") shock is any sudden, unexpected event that shifts the short-run aggregate supply (SRAS) curve. Think oil price spikes, natural disasters, wars that disrupt trade, or a surprise jump in [wages](/ap-macro/key-terms/wages "fv-autolink") or input costs. The defining feature is the direction of the effects. Per EK MOD-2.H.2, a **negative supply shock** (SRAS shifts left) makes output and employment fall while the price level rises. A **positive supply shock** (SRAS shifts right, like a productivity boom or cheaper inputs) makes output and employment rise while the price level falls. That opposite movement of output and prices is what makes supply shocks special. [Demand shocks](/ap-macro/unit-5/phillips-curve/study-guide/tO36uHUjJI2P365apgB4 "fv-autolink") push output and the price level in the *same* direction. Supply shocks split them apart. A negative supply shock is the one scenario in the AD-AS model that produces rising inflation and falling real GDP at the same time, which is called **stagflation**. It's also the source of **cost-push inflation**, inflation driven by higher production costs rather than by excess spending (EK MOD-2.H.3). ## Why It Matters Supply shocks live in **Topic 3.6 (Changes in the AD-AS Model in the Short Run)** in [Unit 3](/ap-macro/unit-3 "fv-autolink"), under learning objective **[AP Macro](/ap-macro "fv-autolink") 3.6.A**, which asks you to explain (with graphs) how output, employment, and the price level respond to an AD or AS shock in the short run. This is one of the most graph-heavy, most-tested skills in the course. If you can't shift SRAS correctly and read off the new equilibrium, Units 4 and 5 get rough fast, because policy questions almost always start with 'an economy experiences a shock...' Supply shocks are also the standard setup for stagflation questions, which test whether you really understand that not all inflation comes from too much demand. ## Connections ### Demand shock (Unit 3) Demand shocks are the other half of Topic 3.6. The fast way to tell them apart on a question: demand shocks move output and the [price level](/ap-macro/key-terms/price-level "fv-autolink") in the same direction, supply shocks move them in opposite directions. If a stem says prices rose AND output fell, it's a negative supply shock, full stop. ### Cost-push inflation (Unit 3) [Cost-push inflation](/ap-macro/unit-3/changes-ad-as-model-short-run/study-guide/dZjop0iV2M7iUQ9Rl1FS "fv-autolink") IS the price-level effect of a negative supply shock. Higher input costs (oil, wages, raw materials) shift SRAS left, pushing prices up from the supply side. EK MOD-2.H.3 pairs it with demand-pull inflation as the two causes of inflation you have to distinguish. ### Aggregate Supply (SRAS) (Unit 3) A supply shock is just a sudden, unexpected version of an SRAS shifter. Anything that changes [production costs](/ap-macro/key-terms/production-costs "fv-autolink"), input prices, or productivity shifts SRAS; when it happens abruptly, economists call it a shock. Knowing the SRAS shifters from earlier in Unit 3 tells you exactly what counts as a supply shock. ### Stabilization policy responses (Units 4-5) Negative supply shocks create the classic policy dilemma. Expansionary policy fixes the output gap but worsens inflation; contractionary policy fights inflation but deepens the recession. Fiscal and monetary policy FRQs love starting from a supply shock precisely because there's no painless fix. ## On the AP Exam Supply shocks show up two main ways. First, MCQs give you a scenario (a spike in oil prices, a drought, a productivity surge) and ask what happens to output and the price level in the short run, or they describe stagflation (rising inflation plus falling real GDP) and ask which shock explains it. The answer to the stagflation version is always a negative supply shock. Second, on FRQs you'll draw a correctly labeled AD-AS graph, shift SRAS the right direction, and show the new equilibrium output and price level, often as the setup before a policy question. The graph mechanics matter: label the axes (PL and real GDP), shift SRAS not AD, and mark both equilibria. You should also be ready to classify inflation as cost-push (supply-side) versus demand-pull (demand-side), since practice questions test that distinction directly. ## Supply shocks vs Demand shock Both shocks change short-run equilibrium, but they leave different fingerprints. A demand shock shifts AD, so output and the price level move together (positive AD shock: both rise; negative: both fall). A supply shock shifts SRAS, so output and the price level move in opposite directions (negative SRAS shock: output falls, prices rise). When a question describes the economy's symptoms instead of naming the shock, check whether output and prices moved together or apart. Together means demand; apart means supply. ## Key Takeaways - A supply shock is an unexpected event that shifts the SRAS curve, like an oil price spike, a natural disaster, or a sudden change in production costs. - A negative supply shock shifts SRAS left, causing output and employment to fall while the price level rises (EK MOD-2.H.2). - A positive supply shock shifts SRAS right, causing output and employment to rise while the price level falls. - Stagflation (rising inflation plus falling real GDP) can only come from a negative supply shock in the AD-AS model, because demand shocks move output and prices in the same direction. - Inflation caused by a negative supply shock is called cost-push inflation, as opposed to demand-pull inflation from rising aggregate demand (EK MOD-2.H.3). - Negative supply shocks create a policy dilemma, since fixing the recession with expansionary policy makes the inflation worse. ## FAQs ### What is a supply shock in AP Macro? A supply shock is a sudden, unexpected event that shifts the short-run aggregate supply (SRAS) curve, such as an oil price spike, a natural disaster, or a jump in wages. A negative shock lowers output and raises the price level; a positive shock does the opposite. ### Do supply shocks always cause inflation? No. Only negative supply shocks raise the price level (that's cost-push inflation). A positive supply shock, like a productivity boom or falling input costs, actually lowers the price level while raising output and employment. ### What's the difference between a supply shock and a demand shock? A supply shock shifts SRAS and moves output and the price level in opposite directions. A demand shock shifts AD and moves them in the same direction. If an exam question says prices rose while real GDP fell, that's a negative supply shock, not a demand shock. ### What causes stagflation on the AP Macro exam? A negative supply shock. When SRAS shifts left, the price level rises while real GDP and employment fall, producing rising inflation and rising unemployment at the same time. No AD shift can create that combination by itself. ### Is a supply shock the same as cost-push inflation? Not exactly, but they're tightly linked. The supply shock is the event (SRAS shifting left from higher costs), and cost-push inflation is the resulting rise in the price level. 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