Causes of Inflation

Why This Matters

Inflation isn't one single phenomenon. It's the result of multiple forces that can push prices up from different directions. On the AP Macroeconomics exam, you need to identify where inflationary pressure originates: Is it coming from the demand side (too much spending chasing too few goods) or the supply side (rising production costs squeezing output)?

This distinction is essential for working with the AD-AS model, predicting policy responses, and explaining real-world economic events. The causes of inflation connect directly to core concepts you'll see throughout the course: aggregate demand shifts, short-run aggregate supply movements, monetary policy transmission, fiscal multipliers, and the quantity theory of money.

When you encounter an FRQ asking why prices rose or what policy to recommend, you need to diagnose the underlying cause first. Know which curve shifts, in which direction, and what the graph looks like for each scenario.

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Demand-Side Causes: Too Much Spending

When aggregate demand grows faster than the economy's productive capacity, prices rise. Consumers, businesses, and governments collectively want more goods and services than the economy can produce at current prices. On a graph, the AD curve shifts right, pushing up both real GDP and the price level in the short run.

Demand-Pull Inflation

• Aggregate demand exceeds aggregate supply. This is the classic "too much money chasing too few goods" scenario.
• Driven by increases in C, I, G, or net exports. Any component of AD can trigger this pressure, especially when the economy is near or at full employment.
• Associated with low unemployment and economic expansion. Tight labor markets give workers bargaining power, which fuels even more spending.

Fiscal Policy Expansion

• Increased government spending or tax cuts shift AD right. Both tools inject purchasing power into the economy.
• The spending multiplier exceeds the tax multiplier. Direct government spending has a larger impact per dollar than an equivalent tax cut because the full amount of new spending enters the economy immediately, while households save a portion of any tax cut.
• Creates inflationary pressure when the economy is already at or above potential output. This is exactly why contractionary fiscal policy is prescribed for inflationary gaps.

Monetary Policy Expansion

• Lower interest rates encourage borrowing and spending. This is the Fed's primary transmission mechanism for stimulating AD.
• An increased money supply reduces the opportunity cost of holding money. Consumers and businesses spend rather than save.
• Risks overheating the economy. If the Fed expands the money supply when output is already near potential, inflation accelerates without lasting GDP gains.

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Supply-Side Causes: Rising Production Costs

When production becomes more expensive, firms reduce output and raise prices. The SRAS curve shifts left, creating the painful combination of higher prices and lower real GDP. This is fundamentally different from demand-pull inflation because output falls rather than rises.

Cost-Push Inflation

• Rising input costs reduce aggregate supply. Higher prices for raw materials, energy, or labor squeeze profit margins.
• SRAS shifts left, raising the price level while reducing output. This creates the distinctive stagflation pattern (stagnant growth + inflation).
• Producers pass increased costs to consumers. Firms protect their margins by raising prices, spreading inflationary pressure through the economy.

Supply Shocks

• Sudden, unexpected disruptions to production capacity. Think natural disasters, geopolitical conflicts, pandemics, or resource scarcity.
• Cause an immediate leftward shift of SRAS. The 1973 OPEC oil embargo is the textbook example: oil prices quadrupled, and U.S. inflation surged while the economy contracted.
• Create policy dilemmas for central banks. Fighting inflation with contractionary policy worsens the output decline, while stimulating output worsens inflation. There's no clean fix.

Decrease in Aggregate Supply

• Structural factors that reduce productive capacity. Labor strikes, new regulatory costs, or loss of productive resources (e.g., farmland destroyed by drought).
• Distinct from temporary shocks. These represent longer-lasting constraints on the economy's ability to produce.
• Results in cost-push inflation with persistent output gaps. Harder to resolve than demand-side inflation because there's no simple "shift AD back" solution.

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Monetary Causes: The Quantity Theory

The quantity theory of money provides a direct link between money supply growth and inflation. The equation is:

$MV = PY$

where M is the money supply, V is the velocity of money (how fast money changes hands), P is the price level, and Y is real output. If V and Y are stable, then increases in M translate directly into higher P.

Increase in Money Supply

• The central bank injects money faster than output grows. This is the fundamental monetary cause of inflation.
• From the quantity equation: if V is constant and Y is at potential, then $\%\Delta M = \%\Delta P$. In other words, the percentage change in the money supply equals the inflation rate.
• Long-run monetary neutrality. In the long run, money supply changes affect only nominal variables (like prices and nominal wages), not real output or real wages.

Currency Devaluation

• A weaker currency makes imports more expensive. This directly raises prices of imported goods and imported inputs used in domestic production.
• The pass-through effect spreads to domestic prices. Firms that rely on imported components raise their prices, and those increases ripple through the economy.
• Often results from excessive money creation or loss of confidence. Currency devaluation frequently accompanies broader inflationary episodes rather than causing them in isolation.

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Expectation and Feedback Effects: Self-Fulfilling Inflation

Once inflation takes hold, expectations about future prices can perpetuate it. When workers and firms anticipate rising prices, they adjust wages and prices preemptively, causing the very inflation they expected. This is why central banks monitor inflation expectations so closely.

Built-In Inflation (Inflation Expectations)

• Expected inflation shifts SRAS left. Workers demand higher nominal wages to maintain their real purchasing power, which raises production costs for firms.
• Firms raise prices to cover anticipated cost increases. This creates a self-reinforcing cycle even if the original demand or supply shock has passed.
• Central bank credibility is crucial. If people trust the Fed to keep inflation around its 2% target, expectations stay "anchored" and this cycle doesn't take off.

Wage-Price Spiral

• Rising wages increase production costs, leading to price increases. The cost-push mechanism feeds back into new wage demands.
• Higher prices prompt demands for even higher wages. The cycle accelerates if nothing breaks it.
• Most dangerous in tight labor markets. When unemployment is low, workers have the leverage to demand raises that match or exceed inflation, keeping the spiral going.

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Quick Reference Table

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Self-Check Questions

1. Which two causes of inflation both shift the AD curve right but use different policy tools? What distinguishes their transmission mechanisms?

2. An economy experiences rising prices and rising unemployment simultaneously. Which type of inflation is this, and which curve shifted in which direction?

3. Using the quantity theory of money ($MV = PY$), explain why rapid money supply growth causes inflation when the economy is at full employment.

4. Compare and contrast demand-pull inflation and cost-push inflation in terms of: (a) which curve shifts, (b) what happens to real GDP, and (c) what happens to unemployment.

5. An FRQ describes workers demanding 5% raises because they expect 5% inflation next year, which then causes firms to raise prices by 5%. What concept does this illustrate, and how would you show this on an AD-AS graph?