“The market is at an all-time high” is a sentence about roughly ten companies. That is not a criticism of the index, which is doing exactly what it was designed to do. It is a warning about what the sentence is taken to mean.
Almost everybody in India knows these two numbers and very few people know how they are constructed, which is a shame, because the construction explains most of the confusing things about them.
What an index is, mechanically
An index is a single number summarising a defined group of shares. Three decisions make it: which companies are in it, how much each one counts, and how the number is scaled.
The Sensex holds thirty companies on the BSE. The Nifty 50 holds fifty on the NSE. They overlap heavily and move almost identically day to day, which is why arguing about which is better is a poor use of anybody's time.
The weighting is where the interesting part lives. Neither index gives its members equal weight. Each is weighted by free-float market capitalisation — the market value of the shares that are actually available to trade, excluding those locked with promoters and other strategic holders.
Two consequences follow. A larger company moves the index more, and a company where promoters hold a very large stake counts for less than its total size suggests, because much of it is not in circulation.
The effect is more concentrated than most people expect. In a fifty-company index weighted this way, the largest handful can account for a substantial share of the entire movement, and the smallest members can have a good year without troubling the number at all. So an index at a record does not mean most shares are doing well. It means the heavy ones are.
The absolute level, meanwhile, means nothing on its own. These numbers are scaled against a base year with an arbitrary starting value, so the level only carries information relative to its own history.
How companies get in, and what inclusion does
Membership is reviewed periodically against published criteria — size, how easily the shares trade, how long the company has been listed, and how much of it is available to buy.
What makes this worth knowing is what happens around a change. Every fund tracking the index has to hold the new entrant and dispose of the departing one, and they have to do it around the same date. That produces real buying and selling driven entirely by a rule rather than by any view on the business.
People routinely misread this. Inclusion is not a verdict on quality — it is a consequence of size and liquidity, both of which are the result of a good run rather than a prediction of the next one. A company enters after it has already grown, which is precisely when its valuation is least attractive.
There is a lesson in the other direction too. A company that leaves an index has usually shrunk considerably before the rule notices, so removal is confirmation of something already visible in the price rather than fresh information.
Price return and total return, and why the difference matters to you
This is the part almost nobody is told, and it changes what you should be comparing your own results against.
The Nifty and Sensex levels quoted in the news are price return figures. They track share prices and nothing else. Dividends paid by the member companies are simply not counted.
The total return version assumes every dividend is reinvested back into the index. Over a year the difference is a percentage point or so — small enough to ignore in conversation. Over twenty years, compounded, it is not small at all. It is one of the larger gaps in Indian personal finance that gets almost no attention.
Where this bites in practice: if you hold an index fund, your holding receives those dividends and reinvests them, so its performance should be compared against the total return version. Comparing it against the price return number shown on television makes your fund look like it is beating the index, when in fact it is tracking a different and higher one. The reverse error is more common and more damaging — somebody comparing an actively managed holding against the price return figure concludes it is doing well, when against the correct benchmark it is behind.
The rule is short: compare like with like, and the like is the total return index.
What the index does not tell you
Four limits worth holding onto, because each one is regularly forgotten in a headline.
It is not the economy. It is a set of large listed companies. Enormous parts of Indian economic activity are unlisted, small, or agricultural, and none of that appears here. The index can rise through a difficult year for most people, and there is no contradiction in that.
“The market fell today” often means the heavy members fell. On plenty of red days the majority of listed shares actually rose, and the broader indices tell a different story from the headline one.
It carries no view. An index does not think a company is good. It holds what the rule says to hold, in the proportion the rule specifies. That mechanical quality is precisely why tracking one is cheap and why it does not need to be clever.
It changes underneath you. The Nifty of 2005 and the Nifty of today share only some members. The long-run chart is not the record of a fixed set of companies — it is the record of a rule that kept replacing weakening members with stronger ones. That survivorship is part of why the line looks the way it does, and it is worth knowing before drawing conclusions from it.
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Index methodology, review criteria and constituents are published by the exchanges and are revised periodically — check the current documents rather than relying on any description here. This is educational material and not advice. We run no tips group and no signal service, we manage nobody's money, and no return is promised on any index or holding mentioned.
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Frequently Asked Questions
What is the difference between the Nifty and the Sensex?
The Sensex holds thirty companies on the BSE, the Nifty 50 holds fifty on the NSE. They overlap substantially and move almost identically day to day. Neither is meaningfully better as a market summary, and the choice between them matters far less than most comparisons suggest.
Does an all-time high mean most shares are rising?
No. Both indices are weighted by free-float market value, so a handful of the largest members drive most of the movement. An index record tells you the heavy companies are doing well; the broader market may be flat or falling underneath it.
What is the total return index?
The version that assumes dividends are reinvested. The figures quoted in the news are price return and exclude dividends entirely. Over a year the difference is about a percentage point; over two decades of compounding it is large, and it is the correct benchmark for comparing an index fund.
Is a stock a good buy because it entered the Nifty?
Inclusion reflects size and liquidity, both of which follow a strong run rather than predict the next one. There is genuine index-fund buying around the change date, but the company enters after it has already grown, which is when its valuation is typically least attractive.
Does the index level itself mean anything?
Only relative to its own history. Both indices are scaled from a base year with an arbitrary starting value, so the absolute number carries no information about whether shares are expensive. Comparing today's level to last year's is meaningful; the number in isolation is not.
Related Reading
- Stock Market for Beginners, for Mumbai
- Owning the index instead of picking
- The two ways to hold an index
- What an index return is worth after inflation
- Free float, and why it decides the weight
Disclaimer: TheFinBaba provides educational content only - this is not investment advice. Trading involves risk of loss.
