Widely read:
Vinayak Pathak/AI-Generated Image
Summary: Investing in market indices provides broad exposure at low risk and cost. However, how diversified your index is matters more than which index you choose to invest in.
Index investing sounds simple until you have to pick one. Sensex, Nifty 50, Nifty 100, Nifty 500, BSE AllCap, Nifty Total Market. All equity indices. All apparently sensible. But they are not six versions of the same thing. They represent very different slices of the market and that difference matters more than most investors realise.
The right question, then, is not just which index delivered the best return. It is: how much of the market does each index actually cover, how dependent is it on a handful of giant companies, and did going broader genuinely reward investors?
Concentration: The number that tells the real story
An index is simply a basket of stocks built using rules. One useful way to size up any index is the weight of its top 10 constituents, or how much of the index is held by its 10 biggest stocks. The higher this number, the more the index rides on a few companies. That is concentration.
Not all indices are the same
While some indices have only a handful of stocks, the rest have a broader investment universe
| Index | What it broadly represents | Weight of the top 10 stocks (%) |
|---|---|---|
| BSE Sensex | 30 largest companies as per market capitalisation | 65.3 |
| Nifty 50 | 50 large-cap stocks | 54.6 |
| Nifty 100 | Wider large-cap universe | 45.4 |
| Nifty 500 | Large, mid and small caps | 32.2 |
| BSE AllCap | Broad market exposure | 30.3 |
| Nifty Total Market | Closest to owning the whole market | 31 |
The Sensex is the most concentrated, as its top 10 stocks alone account for 65.3 per cent of the index. The Nifty 50 is not far behind at 54.6 per cent. In contrast, the top 10 stocks across indices like the BSE AllCap, Nifty 500 and Nifty Total Market account for only 30-32 per cent. Simply put, the broader indices are simply less dependent on a few giants.
Did going wider actually help?
To answer this fairly, it helps to use rolling returns, which are calculated over many overlapping periods rather than a single fixed window. This gives a more honest picture of what investors actually experienced over time. The median return is the middle outcome across all those periods. Standard deviation measures how bumpy the ride was.
More diversification doesn’t always translate to better performance
Having more stocks hasn’t led to significantly better returns or lower volatility for indices
|
|
BSE Sensex | Nifty 50 | Nifty 100 | Nifty 500 | BSE AllCap | Nifty Total Market |
|---|---|---|---|---|---|---|
| Standard deviation | 16.1 | 16.1 | 16.1 | 16 | 16 | 16.1 |
| Median return (%) | 13.1 | 12.9 | 13.2 | 13.2 | 13.5 | 13.4 |
| Returns >16% (% of periods) | 18.3 | 17.9 | 21.2 | 29.5 | 31.3 | 32 |
| Data from August 2011 to March 2026 | ||||||
The first surprise: volatility was nearly identical across all six. Standard deviation sat between 16.0 and 16.1 for every index. Broader did not mean lower risk.
On returns, the gap looks small at first. BSE AllCap led with a median return of 13.5 per cent; Nifty Total Market followed at 13.4 per cent. The Sensex came in at 13.1 per cent, Nifty 50 at 12.9 per cent. Half a percentage point, which is easy to dismiss.
But it is not noise. BSE AllCap and Nifty Total Market each carry roughly 17 per cent in mid-cap stocks and 13 per cent in small-cap stocks. That 30 per cent combined exposure to mid and small caps does real work. Smaller companies tend to grow faster because they have more room to compound. Spread across hundreds of stocks, their individual volatility averages out, which explains why the standard deviation stays flat even as returns nudge higher. Half a per cent, compounded over a decade, is not a rounding error.
The return buckets make this even clearer. BSE AllCap delivered returns above 16 per cent in 31.3 per cent of all rolling periods. The Sensex managed that only 18.3 per cent of the time. More frequent strong-return phases, with no extra turbulence to show for it.
Which index suits whom?
- Sensex / Nifty 50: The simplest starting point. Familiar, well-tracked, easy to understand.
- Nifty 100: A middle path. Broader large-cap exposure without going all-market.
- Nifty 500 / BSE AllCap / Nifty Total Market: For investors who want wider market ownership. Less concentrated, slightly better return profiles, and no visible volatility penalty. Among these, BSE AllCap and Nifty Total Market stand out as strong long-term core holdings.
The bottom line
All index funds do not give you the same market. Some are tightly packed around a few giants. Others spread your money across a far wider base. The data show that broader indices were less concentrated, delivered slightly stronger returns over time, and did not make the journey meaningfully rougher.
The best index is not the one with the loudest name. It is the one whose breadth and behaviour match what you want to own for years.
Also read: Which index fund fits your portfolio?
This article was originally published on April 08, 2026.
Disclaimer: This content is for information only and should not be considered investment advice or a recommendation.
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