Consumer price index is a tool used to determine the regular changes in price of goods and services. What all price changes occurred in a product during a span of short time period.A comprehensive measure used for estimation of price changes in a basket of goods and services representative of consumption expenditure in an economy is called consumer price index.
The calculation involved in the estimation of CPI is quite rigorous. Various categories and sub-categories have been made for classifying consumption items and on the basis of consumer categories like urban or rural areas.