Skip to content

Lesson M01.L04: Real vs Nominal GDP and Price Indices

Module: Introduction to Macroeconomics Level: intro Duration: 30 minutes Learning Objective: Distinguish real from nominal GDP; construct a simple price index; explain why real GDP is the preferred welfare measure. Provenance: OpenStax Macro 3e | Khan Academy Macro

Explanation

When GDP rises from one year to the next, is that because the economy actually produced more, or just because prices rose? To answer this, economists separate GDP into two components:

Nominal GDP is GDP measured in the prices of the current year. If prices double but quantities stay the same, nominal GDP doubles — but nothing extra was produced.

Real GDP is GDP measured in the prices of a fixed base year. By holding prices constant, any change in real GDP reflects a genuine change in the volume of goods and services produced. Real GDP is the preferred measure of economic welfare and living standards.

To convert between them, we use a price index — a number that tracks how much a representative basket of goods costs relative to the base year.

GDP Deflator = (Nominal GDP / Real GDP) × 100

A GDP deflator of 110 means prices are 10% higher than in the base year.

The ABS calculates real GDP using chain-volume measures, with a base year updated periodically (currently 2021–22).

Why does it matter? In 2022, Australia's nominal GDP jumped sharply — partly real growth, partly surging commodity prices (iron ore, coal, LNG). Real GDP strips out the price effect to show how much actual output grew.

Worked Example

Imagine Australia produces only two goods: wheat and iron ore.

Base Year (2020):

Good Quantity Price Value
Wheat 100 tonnes $200/t $20,000
Iron ore 50 tonnes $100/t $5,000
Nominal GDP₂₀₂₀ $25,000

Current Year (2023):

Good Quantity Price Value
Wheat 110 tonnes $240/t $26,400
Iron ore 60 tonnes $140/t $8,400
Nominal GDP₂₀₂₃ $34,800

Real GDP₂₀₂₃ (using 2020 base-year prices):

Good Quantity 2023 Base Price Value
Wheat 110 $200 $22,000
Iron ore 60 $100 $6,000
Real GDP₂₀₂₃ $28,000

GDP Deflator₂₀₂₃ = (34,800 / 28,000) × 100 = 124.3

Prices rose ~24.3%, but real output rose only (28,000 − 25,000) / 25,000 = 12%. Nominal GDP overstates growth.

Common Misconception

Misconception: A rising nominal GDP always means people are better off.

Correction: If prices rise faster than output, nominal GDP increases even as real production stagnates. Real GDP per capita — which strips out inflation and population growth — is the standard measure of changes in average living standards. Australia's real GDP per capita actually fell in 2022–23 despite strong nominal GDP growth, because population grew faster than real output.

Practice Prompts

  1. Nominal GDP = \(2,000bn; GDP Deflator = 125. What is Real GDP? → **Answer:** Real GDP = (2,000 / 125) × 100 = **\)1,600bn**.

  2. In 2021 a simple economy has Nominal GDP = $500bn and Real GDP = $500bn. In 2022, Nominal GDP = $600bn and Real GDP = $540bn. What is the GDP Deflator in 2022? → Answer: (600 / 540) × 100 = 111.1 (prices rose ~11.1%).

  3. Why is real GDP preferred over nominal GDP as a welfare measure? → Answer: Real GDP removes the effect of price changes, so it reflects only changes in the actual volume of goods and services produced. Nominal GDP can rise simply because prices rose, without any improvement in material living standards.

Visual — Nominal GDP vs Real GDP in Australia

Australia: nominal GDP rises faster than real GDP when prices surge Year Index / A$bn (stylised) Nominal GDP Real GDP 2000 2010 2020 2023 2022–23 inflation / commodity boom: nominal GDP pulls away from real GDP. High-inflation period

Figure: Both nominal and real GDP trend upward over time, but nominal GDP can jump much faster when prices rise. The widening gap in 2022–23 illustrates why real GDP is the better measure of changes in actual output.

Further Resources