CPI

Consumer price index; tracks average price changes for a basket of goods and services.

The Consumer Price Index (CPI) is a major economic indicator that measures the average change over time in the prices paid by urban consumers for a market basket of consumer goods and services. It is the most widely watched gauge of inflation in an economy, reflecting the cost of living by tracking price shifts across categories such as food, energy, housing, apparel, transportation, and medical care. To calculate the CPI, government statistical agencies (such as the Bureau of Labor Statistics in the United States) collect thousands of price quotes monthly. They compare the current cost of the representative basket of goods to its cost in a designated base year. The index is typically reported as a percentage change month-over-month or year-over-year, with "Core CPI" often highlighted to show price changes excluding volatile food and energy costs. Investors monitor CPI closely because it directly influences central bank monetary policy. High or rising CPI readings indicate accelerating inflation, which often prompts central banks to raise interest rates to cool the economy, potentially depressing stock and bond prices. Conversely, low or falling CPI readings can signal economic slowdowns or deflationary risks, prompting rate cuts. A common pitfall for investors is failing to distinguish between headline CPI and Core CPI, as short-term commodity price spikes can temporarily distort headline numbers without reflecting long-term inflation trends.

If the market basket of goods and services cost $100 in the base period, the index is set at 100. If the same basket costs $250 today, the current CPI is 250. If the CPI was 240 exactly one year ago, the annual inflation rate is calculated as: ((250 - 240) / 240) 100 = 4.17%.