performance of a given market. For instance if one wants to understand how the stock market has performed over the last 5, 10 or 15 years, one would need to study the performance of each of the stocks listed in the stock market.

Alternatively, it would be easier to construct a representative sample that makes it simple to understand and interpret market performance. Such a sample is termed as an Index. Well-known indices in the Indian equity market are the BSE Sensex and S&P CNX Nifty which reflect the movement of 30 stocks on the Bombay Stock Exchange and 50 stocks on the National Stock Exchange respectively. The BSE Sensex has grown from a base of 100 in 1979-80 to over 4000 in recent times.