Two benchmarks, two exchanges, one market — and a country whose exchanges both now rank among the ten largest in the world by listed value.
India runs two headline indexes on two exchanges. The Sensex — the S&P BSE Sensex — dates to 1986 and covers 30 companies on the Bombay Stock Exchange, Asia's oldest. The Nifty 50 launched in 1996 on the newer National Stock Exchange and covers 50.
Both are float-adjusted capitalization weighted, both are dominated by the same large financial, technology and energy groups, and they move closely together. The split is institutional history rather than methodological disagreement.
The NSE was created in 1992 explicitly to introduce electronic trading and break the older exchange's practices, and it succeeded — it now dominates trading volume, particularly in derivatives, where Indian index options have become extraordinarily active by global standards.
The Sensex retains the longer history and the public familiarity, much as the Dow does in the United States. When a general audience hears an Indian market number, it is usually the Sensex; when money is traded against an index, it is usually the Nifty.
Both are heavily weighted toward financials — private-sector banks in particular — alongside information technology services, energy and consumer goods. The concentration in a handful of large conglomerate groups is high by developed-market standards.
Retail participation has grown substantially through systematic monthly investment plans, which channel steady domestic flows into equity funds and have made the market less dependent on foreign institutional money than it once was.
The Nifty 50 is broader and carries more traded volume. The Sensex has the longer series and more public recognition. They correlate closely enough that the choice rarely matters for direction.
The NSE was established in 1992 to modernize trading through electronic execution. It took most of the volume, but the BSE retained its listings and its index.