CPI, Real GDP, and the GDP Deflator: Economic Metrics
Understanding Key Economic Indicators: CPI and GDP
What is the Consumer Price Index (CPI)?
The Consumer Price Index (CPI) determines the general price level, considering only the prices of goods and services purchased directly by consumers. It is an index that measures inflation—a widespread and sustained rise in the prices of consumer goods.
How is the CPI Calculated?
The calculation of the CPI involves several steps:
- Basket of Goods: A list of frequently consumed goods and services (the "basket of goods") is compiled.
- Price Comparison: The average market prices of these selected items are determined for the study period and compared with the prices they had in a reference period. The resulting variation is then expressed.
- Weighting: A representative set of families is selected, and a survey (such as the Survey of Family Budgets, EPF) is conducted to determine the average percentage of income allocated to each asset in the basket.
- Final Calculation: The CPI is calculated using the collected data and a specific formula.
Impact of CPI Rise on Businesses
A rise in the CPI can cause an increase in the price of production factors, such as raw materials and energy sources. This consequently increases production costs, which could reduce supply and, therefore, increase the selling price of products in the market. The final effect is higher inflation.
Real GDP, Nominal GDP, and the GDP Deflator
Distinguishing Real GDP from Nominal GDP
When Gross Domestic Product (GDP) increases over time, the rise may be due to higher prices or an actual increase in the production of goods and services. To avoid this ambiguity, Real GDP is used.
- Nominal GDP: Registers the total production of all final goods from one country using current prices of the year.
- Real GDP: Values goods and services at constant prices (prices fixed to a base year). This eliminates the effect of inflation, allowing economists to check whether production has genuinely increased or declined.
For this reason, Real GDP is considered a better measure of true economic growth, reflecting the real increase in production without accounting for price rises.
The GDP Deflator
The GDP Deflator is the "price" of GDP—a price index that measures the average price of the components of GDP in relation to a base year. It is the result of the ratio between Nominal GDP (measured in current monetary units) and Real GDP (measured in constant currency units).
GDP Deflator Formula
The formula for calculating the GDP Deflator is:
Deflator = Nominal GDP / Real GDP