Index Numbers are the indicators which reflect the changes over a specified period of time in price of different commodities, production, sales, cost of living etc... Index Numbers are statistical methods used to measure the relative change in the level of a variable or group of variables with respect to time, geographical location or other characteristics such as income, profession etc. The variables may be
(i) The price of a particular commodity. For example gold, silver, iron (or) a group of commodities. For example consumer goods, household food items etc..
(ii) The volume of export and import, agricultural and industrial production.
(iii) National income of a country, cost of living of persons belonging to a particular income group.