What Do You Mean by Index Number

Learn about index numbers, a statistical measure used to track changes in variables over time or across different groups. Explore types, uses, examples, and case studies.


An index number is a statistical measure that represents changes in variables over time or across different groups. It is used to show relative changes in prices, quantities, or other economic indicators. Index numbers are widely used in economics, finance, and other fields to monitor trends and make comparisons.

Types of Index Numbers

  • Price Index: Measures changes in the prices of goods and services.
  • Quantity Index: Measures changes in the quantities of goods and services.
  • Composite Index: Combines price and quantity changes into a single index.

Uses of Index Numbers

Index numbers are used for various purposes, such as:

  • Tracking inflation
  • Comparing living standards
  • Measuring economic growth
  • Assessing market performance

Example of Index Number

One of the most well-known index numbers is the Consumer Price Index (CPI), which measures changes in prices paid by consumers for goods and services. The CPI is used to track inflation and adjust wage rates, tax brackets, and social security benefits.

Case Study: S&P 500 Index

The S&P 500 Index is a stock market index that tracks the performance of 500 large-cap US companies. It is widely used as a benchmark for the overall stock market and a key indicator of economic health. Investors use the S&P 500 Index to assess market trends and make investment decisions.

Statistics on Index Numbers

According to the Bureau of Labor Statistics, the CPI for All Urban Consumers (CPI-U) increased by 0.6% in March 2021, indicating rising inflation. This rise was driven by higher prices for gasoline, food, and shelter.


Index numbers play a crucial role in measuring changes in economic variables and monitoring trends over time. They provide valuable insights for policymakers, businesses, and investors to make informed decisions. Understanding index numbers is essential for interpreting economic data and navigating the complexities of the modern economy.

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