GDP price deflator: Nominal output vs. real output

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Discounting the effects of inflation.

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Suppose you tune into the financial news to hear that the economy’s gross domestic product (GDP) grew by 6.5% last quarter. Sounds like a productivity boom, right? But then you hear those same experts mention the “real GDP” figure, which fell by 1.6%. So what’s going on?

The answer lies in a key measure called the GDP price deflator—a metric that tells you how much of a GDP change is caused by price inflation rather than actual growth in goods and services.

If this scenario sounds familiar, that might be because it happened in the first quarter of 2022. According to data from the Bureau of Economic Analysis (BEA), prices rose by about 15.11% during that quarter. The U.S. economy was still recovering from the COVID-19 lockdowns, and price hikes driven by global supply chain disruptions fueled much of the GDP increase.

So while the economy’s real production fell, its GDP figure grew, driven by inflation rather than actual economic expansion. In other words, the “boom” was in prices, not in real economic growth. This underscores the importance of the deflator metric, which isolates the effects of prices from productivity.

The GDP price deflator formula is straightforward:

GDP price deflator = (nominal GDP / real GDP) x 100

Nominal GDP is the total dollar value of the goods and services produced by the economy during a specified period. If you need a refresher on the GDP formula, it’s the total of consumption, investment, government spending, and net exports, or C + I + G + (X – M). Nominal GDP includes real growth plus the effects of inflation.

Real GDP is the total dollar value of the goods and services produced in an economy, but adjusted for inflation. It’s measured in constant dollars relative to a base year—showing real economic growth without the distortion of rising prices.

In essence, the GDP price deflator tells us how much of the GDP’s growth comes from inflation rather than actual economic output (see figure 1).

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Figure 1: HOW REAL IS GDP? In the post-pandemic economy of the early 2020s, the first major period of inflation in several decades meant that much of the economic growth came from higher prices, not actual expansion. In economic terms, the real GDP was much lower than the nominal GDP.

Data source: U.S. Bureau of Economic Analysis, Gross Domestic Product [GDP], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/GDP, June 4, 2025.

Suppose the U.S. produced $20 trillion worth of goods and services in one year (its nominal GDP). The next year, the nominal GDP rose to $22 trillion—an increase of 10%. Suppose, however, that the BEA calculated that the total goods and services produced—relative to what was produced during the base year—was only $21 trillion.

Let’s apply the formula: GDP price deflator = (22 ÷ 21) x 100 = 104.76, or 4.76%.

This tells us that of the 10% in nominal GDP growth, 4.76% is due to inflation.

The difference between these inflation reports is in their scale and areas of focus:

In contrast, the GDP price deflator covers all final goods and services, including investment products, government services, and exports. It’s much more comprehensive in scope when measuring overall price changes in the economy.

You can probably guess the importance of the GDP price deflator to economists, government institutions, and policymakers responsible for making monetary and/or fiscal policy decisions. But how can you, as an investor, use this metric to help inform or improve your investment decisions? Here are a few ideas:

As comprehensive as this metric is, there are a few important limitations to keep in mind, especially for investors. The biggest one is timing: the data lags and is revised quarterly, just like GDP itself. So don’t be surprised if the number shifts slightly next quarter—potentially enough to affect your forecasts.

Another challenge is breadth. Because the GDP deflator spans the whole economy, it doesn’t offer much detail on specific sectors that affect consumers more directly. For a sharper view of category-level inflation, it’s best to pair it with CPI, PPI, and PCE data to get a better read on inflation across particular categories.

Next time you come across the headline GDP (i.e., nominal GDP) figure, remember that there’s a little more to the story, especially if you’re using this data as part of your portfolio strategy. Think of the GDP price deflator as something of a reality check—one that helps you separate the noise from the signal when gauging the economy’s true pulse.