
Index funds: fewer stocks matter more than you think
Subscribe to enjoy similar stories.The shift towards passive investing is one of the defining trends of this decade. According to NSE Indices’ Nifty Passive Insight report, released in March, assets under management (AUM) in passive schemes stood at ₹14.84 trillion as of end of February, up ninefold from ₹1.63 trillion in 2020.The passive universe now spans 677 schemes and 54 million folios, with 67% of AUM in equity, and more than half of that benchmarked to the Nifty 50.The foundation traces back to Nobel laureate William Sharpe, who argued in his 1991 paper The Arithmetic of Active Management that, after costs, the average actively managed dollar must underperform its passive counterpart.
The Nifty 50 offers exposure to India’s largest companies at expense ratios of 0.10–0.20%, a fraction of the 1.00–1.75% typically charged by active large-cap funds. Low-cost diversification sits at the core of index investing.A useful starting point is the broader market.NSE’s April Market Pulse report measures India’s overall market concentration using the Herfindahl-Hirschman Index (HHI).
That figure has fallen from 202 in 1995 to 81 in 2025, reflecting a steady dispersion of market capitalisation across a wider set of companies. The market as a whole is becoming less concentrated over time.
The question for an index investor is whether that dispersion shows up in their fund.The HHI for the Nifty 50, calculated as the sum of the squares of constituent weights, averages 457 across annual factsheets from March 2017 to March 2026. The corresponding figure for the Nifty Next 50 is 244.By conventional thresholds, where an HHI above 1,500 signals concentration, neither index appears concentrated at the stock level.
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