An index number is a statistical measure that represents changes in the magnitude of related variables over time, often expressed as a percentage.

They summarize the changes in prices, quantity, or value of goods to inform economic policies and understand economic trends.

Price index numbers measure the change in the price of a specified list of goods over time.

It calculates an index using the formula: P01 = (Σ P1 / Σ P0) * 100, where P1 = current period prices and P0 = base period prices.

A weighted index number accounts for the relative importance of items, using weights to reflect their significance in the index.

It uses base period quantities as weights to calculate the index, capturing how much expenditure on the base period basket would change due to price variations.

It uses current period quantities as weights, reflecting how much expenditure on the current basket would need to change due to earlier prices.

Using the formula: P01 = (Σ (P1 / P0) * 100) / n, where n is the number of commodities, providing an average measure of price changes.

CPI measures the average change in retail prices of a basket of goods and services, reflecting the cost of living.

WPI indicates the change in the price level of goods at the wholesale stage, reflecting price trends before retail.

CPI (2001=100) being 277 in December 2014 means Rs 100 in 2001 is equivalent to Rs 277 for a similar basket in 2014.

Inflation is primarily measured using CPI and WPI, by analyzing the percentage changes in price levels over time.

Ensure the chosen items in the index are representative of the population it measures, as differing importance may skew results.

Poor reliability can result in misleading index numbers, skewing economic analysis and decisions.

Ignoring the significance of base year selections can lead to misinterpretation of quantitative changes.

Index numbers support decisions in wage negotiations, inflation tracking, and formulating fiscal and monetary policies.

An index above 100 indicates a need for wage adjustments to maintain purchasing power relative to the cost of living.

Weights reflect the importance of each commodity, ensuring the index accurately represents overall price changes.

Trends provide insights into overall economic conditions, inflation, and consumer behavior over time.