Updated: Real versus Nominal GDP and the GDP Deflator

A nation’s GDP measure’s the value of its output of goods and services in a particular period of time. Gross Domestic Product is expressed in dollar terms, which means that if the price of goods and services rise, a country’s nominal GDP figure will increase. The problem with this is that an increase in the nominal (numerical) value of a country’s output can increase when price levels rise, even if the actual level of output remains the same.

For this reason, it is important to adjust a nation’s nominal GDP for any changes in the price level that occur between two periods of time. Once nominal GDP is adjusted for inflation or deflation, we arrive at real GDP, which is a much more accurate measurement of the actual level of output in a nation, adjusting for any changes in prices.

This lesson will define nominal and real GDP and use a numerical example to illustrate why measuring nominal GDP produces a false impression of the actual level of output a nation is producing from one year to the next. We will then use a simple formula to determine the GDP deflator, the price index that allows us to adjust nominal GDP to arrive at real GDP.

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