Real versus nominal GDP
GDP can rise because more is produced or because prices rise. Separating the two is essential for understanding growth.
Nominal GDP
Nominal GDP values output at current prices. If prices double while output stays the same, nominal GDP doubles too, although nobody is better off. Comparing nominal GDP across years therefore mixes real changes with price changes.
Real GDP
Real GDP values output at the prices of a fixed base year, so it changes only when quantities change. It is the right measure for economic growth. Statistical agencies today use chain-weighted methods that update the base frequently, but the idea is the same.
The GDP deflator
The GDP deflator is a price index: \(\text{deflator} = \frac{\text{nominal GDP}}{\text{real GDP}} \times 100\). If nominal GDP is 1,100 and real GDP is 1,000, the deflator is 110, meaning prices are 10% higher than in the base year.
Worked example
An economy produces only pizzas. In 2020 (the base year), it makes 100 pizzas at 10 dollars: nominal and real GDP are 1,000. In 2025 it makes 110 pizzas at 12 dollars. Nominal GDP is 1,320; real GDP at 2020 prices is 1,100. Real growth is 10%; the deflator is 1,320/1,100 x 100 = 120.
Growth rates
The growth rate of real GDP is \(\frac{\text{real GDP}_t - \text{real GDP}_{t-1}}{\text{real GDP}_{t-1}} \times 100\%\). A useful approximation: nominal growth is roughly real growth plus inflation. If nominal GDP grows 6% and prices rise 4%, real GDP grows about 2%.
GDP per capita
To compare living standards, divide GDP by population: GDP per capita. A large economy like India has high total GDP but much lower GDP per person than smaller, richer economies such as Switzerland. Growth in per capita GDP is the best simple measure of rising average living standards.
Purchasing power parity
Comparing GDP across countries using market exchange rates can mislead, because many goods, especially services, are cheaper in poorer countries. Purchasing power parity (PPP) adjusts for these price differences. By PPP measures, China's economy is larger than the United States', while at market exchange rates the US is larger.
Beyond GDP
GDP is not a measure of well-being. It ignores leisure, inequality, environmental damage, and unpaid care, and counts spending on disasters as output. Alternatives include the Human Development Index (combining income, education, and life expectancy) and measures of life satisfaction and environmental sustainability.
Key takeaways
Nominal GDP uses current prices; real GDP uses constant prices and measures real growth. The GDP deflator is nominal over real times 100. Nominal growth is roughly real growth plus inflation. GDP per capita compares living standards; PPP adjusts for price differences across countries. GDP is not a complete measure of well-being.
Flashcard
Output at current prices
Check your understanding
Nominal GDP rose 7% and the GDP deflator rose 5%. Approximately how much did real GDP grow?