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4.3.2 components of AD and their meanings: AD = C + I + G + (X – M)

4.3.2 components of AD and their meanings: AD = C + I + G + (X – M)

Components of Aggregate Demand

Definition

Aggregate demand (AD): the total planned spending on domestic output at each average price level, equal to C + I + G + (X − M).

Net exports (X − M): the value of exports minus the value of imports, which may be positive or negative.

What Each Component Measures

  1. Consumption (C) is household spending on goods and services, normally the largest single component of AD.
  2. Investment (I) is firms' spending on capital goods such as machinery and buildings.
  3. Government spending (G) is state spending on goods and services such as schools and roads; it excludes transfer payments, which are not spending on output.
  4. Net exports (X − M) are exports minus imports, added because only spending on domestic output counts.
Key Idea
  • Consumption is normally the largest single component of AD.
  • Net exports can be positive or negative, so they can add to or subtract from AD.

Why Imports Are Subtracted

  1. Exports (X) are added because they are foreign buyers' spending on domestic output.
  2. Imports (M) are subtracted because they are domestic spending on foreign output, which is not part of domestic production.
  3. So only the net figure, X − M, belongs in AD.

Worked Calculation

Example
  • An economy plans C = £600bn, I = £150bn, G = £200bn, X = £120bn and M = £140bn for one year.
AD=C+I+G+(X−M) AD = C + I + G + (X - M) AD=C+I+G+(X−M) AD=600+150+200+(120−140) AD = 600 + 150 + 200 + (120 - 140) AD=600+150+200+(120−140) AD=950+(−20)=930 AD = 950 + (-20) = 930 AD=950+(−20)=930
  • Net exports of X − M = −£20bn pull AD below domestic spending, so AD = £930bn for that year.

Why the Identity Matters

  1. The identity measures planned spending across the whole economy, not one market.
  2. A change in any single component changes total AD, ceteris paribus.
  3. So the identity is the starting point for all AD–AS analysis.
Exam technique
  • Write the identity in full as AD = C + I + G + (X − M).
  • Show your working when you calculate net exports and the total.
Common Mistake
  • Do not add imports to AD; they are subtracted.
  • Do not leave net exports out of the identity.
Self review
  • State the AD identity in full.
  • What does each of C, I, G and (X − M) measure?
  • If C = £500bn, I = £100bn, G = £150bn, X = £90bn and M = £110bn, what is AD?
  • Why are imports subtracted rather than added?
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Diagram showing consumption, investment, government spending, and net exports flowing into the aggregate demand identity

Aggregate demand is the total planned spending on domestic output at each average price level. It is measured across the whole economy, not just one market.

The identity is:

AD=C+I+G+(X−M) AD = C + I + G + (X - M) AD=C+I+G+(X−M)

Consumption (CCC) is household spending, investment (III) is firms' spending on capital goods, and government spending (GGG) is state spending on goods and services. Net exports (X−M)(X - M)(X−M) are exports minus imports.

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What is the identity for aggregate demand?

4.3.2 components of AD and their meanings: AD = C + I + G + (X – M) Revision Guide

  1. Intl A Level
  2. /Economics
  3. /4.3.2 components of AD and their meanings: AD = C + I + G + (X – M)

Revision notes for CIE Intl A Level Economics 4.3.2 components of AD and their meanings: AD = C + I + G + (X – M): explanations and worked examples.