2.3.12 Index Funds & ETFs

Matching the market instead of trying to beat it

An index fund buys the same securities as its target index, in roughly the same proportions, so its performance should closely mirror that index minus a small cost for running the fund. This is a fundamentally different goal from an actively managed fund, which is trying to outperform its benchmark rather than simply match it.

An index fund is a mutual fund that replicates a specific market index by holding the same securities in the same proportions as the index. A Nifty 50 index fund holds all 50 stocks of the Nifty 50 in their free-float market capitalisation weights. The fund does not attempt to pick winners or time the market; it simply mirrors the index as closely as possible. An ETF (Exchange Traded Fund) does the same thing but trades on the stock exchange like a share, with prices fluctuating throughout the trading day.

ETFs versus index mutual funds

An ETF, or exchange-traded fund, follows the same passive philosophy as an index fund but trades on a stock exchange throughout the day like a share, requiring a demat and trading account. An index mutual fund is bought and sold at end-of-day NAV like any other mutual fund, without needing a trading account. The underlying strategy behind both can be functionally similar even though the buying mechanics differ.

The primary advantage is cost. Index funds have expense ratios of 0.05-0.30% in India, compared to 0.50-1.50% for actively managed funds. Over 20-25 years, this fee difference compounds into a substantial wealth gap. The secondary advantage is simplicity: you get broad market exposure without needing to evaluate fund managers, research teams, or investment processes. The performance will closely track the index, minus a small tracking error and the expense ratio.

Tracking error measures how closely the fund's returns follow the index. A well-run index fund should have an annualised tracking error below 0.5%. Tracking error arises from cash drag (funds must hold a small cash balance for redemptions), transaction costs during index reconstitution, and imperfect replication timing. When comparing index funds tracking the same index, the one with the lowest tracking error and the lowest expense ratio is the better choice, since the portfolios are otherwise identical.

ETFs require a demat account and are bought and sold through a stockbroker at market prices. The market price of an ETF can deviate from its NAV during the trading day (a premium or discount), and thinly traded ETFs can have wide bid-ask spreads that add to the effective cost. For most retail investors in India, an index mutual fund is simpler and more convenient than an ETF, avoiding the need for a demat account and eliminating the risk of buying at a premium to NAV.

Why tracking error matters

A well-run index fund should show a very small tracking error, meaning its returns closely mirror the target index rather than drifting away from it. A larger tracking error can point to higher costs, less efficient cash management, or execution issues inside the fund, and it is one of the more important things to check when comparing two index funds tracking the same underlying index.