Index Numbers: Definition, Characteristics, Uses, Types

Index Number is a statistical tool used to measure the relative change in a variable or a group of related variables over time, across regions, or between different conditions. It simplifies comparison by converting values into a standardized form. Index numbers are typically used to track changes in economic variables like prices, quantities, and values, and help in measuring inflation, production levels, or economic growth.

The formula for an index number is typically:

Index Number = [Value in Current Period / Value in Base Period] × 100

Features of Index Numbers:

(i) Index numbers are a special type of average.

Whereas mean, median and mode measure the absolute changes and are used to compare only those series which are expressed in the same units, the technique of index numbers is used to measure the relative changes in the level of a phenomenon where the measurement of absolute change is not possible and the series are expressed in different types of items.

(ii) Index numbers are meant to study the changes in the effects of such factors which cannot be measured directly.

For example, the general price level is an imaginary concept and is not capable of direct measurement. But, through the technique of index numbers, it is possible to have an idea of relative changes in the general level of prices by measuring relative changes in the price level of different commodities.

(iii) The technique of index numbers measures changes in one variable or group of related variables.

For example, one variable can be the price of wheat, and group of variables can be the price of sugar, the price of milk and the price of rice.

(iv) The technique of index numbers is used to compare the levels of a phenomenon on a certain date with its level on some previous date (e.g., the price level in 1980 as compared to that in 1960 taken as the base year) or the levels of a phenomenon at different places on the same date (e.g., the price level in India in 1980 in comparison with that in other countries in 1980).

Uses of Index numbers:

• Index numbers are used in the fields of commerce, meteorology, labour, industry, etc.

• Index numbers measure fluctuations during intervals of time, group differences of geographical position of degree, etc.

• They are used to compare the total variations in the prices of different commodities in which the unit of measurements differs with time and price, etc.

• They measure the purchasing power of money.

• They are helpful in forecasting future economic trends.

• They are used in studying the difference between the comparable categories of animals, people or items.

• Index numbers of industrial production are used to measure the changes in the level of industrial production in the country.

• Index numbers of import prices and export prices are used to measure the changes in the trade of a country.

• Index numbers are used to measure seasonal variations and cyclical variations in a time series.

A collection of index numbers for different years, locations, etc., is sometimes called an index series.

• Simple Index Number: A simple index number is a number that measures a relative change in a single variable with respect to a base.

• Composite Index Number: A composite index number is a number that measures an average relative changes in a group of relative variables with respect to a base.

Types of Index Numbers:

The following types of index numbers are usually used: price index numbers and quantity index numbers.

1. Price Relative:

A price relative measures the change in the price of a commodity or group of commodities over time. It reflects how the price of a product has changed compared to its price in the base period.

• Formula:

Price Relative = [Price in Current Period / Price in Base Period] × 100

2. Quantity Relative:

A quantity relative measures the change in the quantity or volume of goods produced or consumed. It shows how much more or less of a commodity is available compared to a base period.

• Formula:

Quantity Relative = [Quantity in Current Period / Quantity in Base Period] × 100

3. Value Relative:

Value relative measures the change in the value of a commodity or a group of commodities, considering both price and quantity changes. It combines the effects of price and quantity variations on the total value.

• Formula:

Value Relative = [Value in Current Period / Value in Base Period] × 100