GDP deflator

When comparing GDP between years, nominal GDP and real GDP capture different elements of the change. Nominal GDP captures both changes in quantity and changes in prices. Real GDP, on the other hand, captures only changes in quantity and is insensitive to the price level. Because of this difference, after computing nominal GDP and real GDP a third useful statistic can be computed. The GDP deflator is the ratio of nominal GDP to real GDP for a given year minus 1. In effect, the GDP deflator illustrates how much of the change in the GDP from a base year is reliant on changes in the price level.
For example, let's calculate, using , the GDP deflator for Country B in year 3, using year 1 as the base year. In order to find the GDP deflator, we first must determine both nominal GDP and real GDP in year 3.

Nominal GDP in year 3 = (10 X $2) + (9 X $6) = $74
Real GDP in year 3 (with year 1 as base year) = (10 X $1) + (9 X $6) = $64
The ratio of nominal GDP to real GDP is ( $74 / $64 ) - 1 = 16%.

This means that the price level rose 16% from year 1, the base year, to year 3, the comparison year. Rearranging the terms in the equation for the GDP deflator allows for the calculation of nominal GDP by multiplying real GDP and the GDP deflator. This equation demonstrates the unique information shown by each of these measures of output. Real GDP captures changes in quantities. The GDP deflator captures changes in the price level. Nominal GDP captures both changes in prices and changes in quantities. By using nominal GDP, real
GDP, and the GDP deflator you can look at a change in GDP and break it down into its component change in price level and change in quantities produced.