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Lesson M07.L03: Factors Shifting the Aggregate Demand Curve

Module: Aggregate Demand and Aggregate Supply; Macroeconomic Policy Level: intro Duration: 30 minutes Learning Objective: Identify the demand-side factors that shift the AD curve. Data as of: 2023 Provenance: OpenStax Macro 3e | Khan Academy Macro

Explanation

A movement along the AD curve happens when the price level changes. A shift in the entire AD curve happens when something other than the price level causes total spending to change at every price level.

AD = C + I + G + NX. Any factor that raises or lowers one of these components at a given price level shifts the curve.

Factors that shift AD right (increase demand):

  • Consumer confidence rises: Households spend more (โ†‘C). In Australia, the Westpacโ€“Melbourne Institute Consumer Sentiment Index tracks this.
  • Business investment increases: A tax cut for businesses or falling interest rates boost capital spending (โ†‘I).
  • Fiscal stimulus: The federal government increases spending or cuts taxes (โ†‘G or โ†‘C via disposable income).
  • Monetary easing: The RBA cuts the cash rate โ†’ borrowing cheaper โ†’ โ†‘I and โ†‘C.
  • Export boom: Rising commodity prices (e.g., iron ore) raise export revenues โ†’ โ†‘NX.
  • Exchange rate depreciation: A weaker AUD makes Australian exports cheaper and imports dearer โ†’ โ†‘NX.

Factors that shift AD left (decrease demand): The reverse of any of the above: falling confidence, tighter fiscal policy (budget cuts or tax rises), monetary tightening (RBA rate hikes), or a fall in export demand.

A key distinction: fiscal policy operates directly through G and tax changes, while monetary policy operates indirectly by changing interest rates, which then affect C and I.

Worked Example

Scenario: The RBA raises the cash rate from 4.10% to 4.35% (as occurred in November 2023) to reduce inflationary pressure.

Step 1: Identify the transmission mechanism.
Higher cash rate โ†’ commercial banks raise mortgage and business loan rates โ†’ borrowing costs rise โ†’ households reduce spending on credit (โ†“C) and firms reduce investment (โ†“I).

Step 2: Quantify (simplified).
Suppose the rate rise reduces household consumption by $15 billion and business investment by $10 billion at every price level.

Reduction in AD = ฮ”C + ฮ”I = โˆ’\(15b + (โˆ’\)10b) = โˆ’$25 billion

Step 3: Apply the multiplier (simplified, multiplier = 2).
Final shift in AD = โˆ’\(25b ร— 2 = **โˆ’\)50 billion**

The entire AD curve shifts left by approximately $50 billion.

Step 4: Interpret.
At the original price level, real GDP demanded falls by $50 billion. If the economy was overheating (above Y*), this shift helps return output to potential and eases inflationary pressure โ€” the RBA's intended goal.

Common Misconception

Misconception: A rise in the price level shifts the AD curve to the left.

Correction: A rise in the price level causes a movement along the existing AD curve (to a lower quantity of real GDP demanded) โ€” not a shift of the curve itself. The curve only shifts when a non-price-level factor changes total spending. Confusing movements along a curve with shifts of the curve is one of the most common errors in macro principles.

Practice Prompts

  1. In 2020 the Australian federal government spent approximately $70 billion on the JobKeeper program. Using AD components, explain why this shifted AD to the right. โ†’ Answer: JobKeeper was a government transfer that kept workers' incomes up, sustaining household consumption (โ†‘C). It also substituted for government spending (โ†‘G component). Both effects raised total spending at every price level, shifting AD right.

  2. If the AUD depreciates from 0.75 USD to 0.65 USD, what happens to Australia's net exports and the AD curve? โ†’ Answer: A weaker AUD makes Australian exports cheaper for foreign buyers (exports โ†‘) and imports more expensive for Australians (imports โ†“). Net exports rise โ†’ AD shifts right.

  3. Distinguish between a fiscal policy tool and a monetary policy tool that could both shift AD to the right. โ†’ Answer: Fiscal policy example: the federal government increases infrastructure spending (โ†‘G). Monetary policy example: the RBA cuts the cash rate, reducing borrowing costs and stimulating investment (โ†‘I) and consumption (โ†‘C). Both shift AD right but through different channels.

Further Resources