The GDP deflator is a measure used to track inflation by comparing the current prices of all domestically produced goods and services to the prices of those same goods and services in a base year (Mankiw, 2024). It is an easy way to isolate "price changes" from "production changes."
The Formula
To calculate the GDP deflator, you use the following formula:
Key Definitions
Nominal GDP uses current prices, so changes in the value of goods and services can reflect both changes in production and changes in prices. Real GDP adjusts for changes in the price level, allowing economic output to be measured more accurately over time. Since real GDP accounts for inflation, it provides a clearer measure of changes in actual production.
The market value of all final goods and services produced within a country in a given period, measured at current prices (i.e., not adjusted for inflation).
The market value of all final goods and services produced within a country in a given period, adjusted for inflation by using constant prices from a base year.
- If the Deflator is greater than 100: Prices have risen on average compared to the base year (inflation).
- If the Deflator is less than 100: Prices have fallen on average compared to the base year (deflation).
- If the Deflator is 100: The price level is the same as the base year.
Example
The Scenario: A Simple Economy
Imagine an economy that only produces two goods: Apples and Oranges.
Nominal GDP uses current-year prices.
- Year 1 (Nominal): (10 x $1) + (5 x $2) = $10 + $10 = $20
- Year 2 (Nominal): (10 x $2) + (5 x $3) = $20 + $15 = $35
Real GDP uses base-year prices (Year 1) applied to the current production quantities.
- Year 1 (Real): This is the base year, so it remains $20
- Year 2 (Real): (10 apples x $1) + (5 oranges x $2) = $10 + $10 = $20
Note: Real GDP is the same for both years because production quantities didn't change, only prices did.
Now, use the standard formula:
A result of 175 tells us that prices in Year 2 are 75% higher than they were in the base year.
Mankiw, N. G. (2024). Principles of Economics. Cengage Learning.
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