When should you switch an index fund? 4 things investors must check before moving to another fund

Index funds are designed to be simple. They track a market index such as the Nifty 50, allowing investors to participate in the benchmark without trying to pick winning stocks. But simplicity does not mean every index fund tracking the same benchmark will deliver identical returns.

Small differences in costs, execution and portfolio management can cause one fund to consistently lag its benchmark more than another. This raises an important question for investors. When does the difference become large enough to justify switching from one index fund to another?

According to Anshi Shrivastava, Head – Personal Finance Training at 1 Finance, the primary reason to switch should be a fund’s ability to track its benchmark, rather than short-term differences in returns or marketing claims.

Tracking difference is more important than chasing the lowest-cost fund

“An index fund has only one job, to copy a benchmark as closely as possible,” Shrivastava said.

Investors should therefore look at tracking difference, which is the gap between the return delivered by the index and the return delivered by the fund over a period.

For example, if the Nifty 50 rises 12% in a year but an index fund returns 10.5%, the tracking difference is 1.5 percentage points. This difference directly affects what an investor earns.

Investors should also look at tracking error. While tracking difference shows the gap in returns over a period, tracking error measures how consistently the fund’s returns deviate from the index.

A fund could have a relatively small tracking difference over a year while still having a high tracking error if it frequently moves ahead of or behind the index during the year. A fund with low tracking error, on the other hand, tends to stay closer to the index on a day-to-day basis.

Both can be affected by factors such as idle cash, delays in rebalancing when the index changes, trade execution and the fund’s expenses.

Shrivastava recommends comparing tracking difference and tracking error across funds tracking the same index over a three-to-five-year period. If one fund consistently trails its benchmark by a wider margin than its peers, it could indicate a structural problem in how the fund is being managed.

Don’t switch just because another index fund has a lower expense ratio

Expense ratio matters for index funds because the objective is to replicate the benchmark at a low cost. But investors should not automatically choose the fund with the lowest expense ratio.

Most index funds tracking major benchmarks in India charge roughly 0.05% to 0.4% annually, according to Shrivastava. The difference between two well-managed funds can therefore be quite small.

For example, the difference between a fund charging 0.10% and another charging 0.15% is just 0.05 percentage points. On a ₹5 lakh investment, that is roughly ₹250 a year, before considering compounding.

Shrivastava said expense ratio becomes more meaningful when the difference is large and sustained, roughly 0.3 to 0.5 percentage points or more between funds tracking the same index, particularly over a decade or longer.

That means a fund with a slightly higher expense ratio could still be the better choice if it tracks the index more closely.

“Investors who chase the cheapest fund while ignoring tracking errors are optimizing for the wrong number,” she said.

Does a bigger index fund mean a better index fund?

A large AUM can offer some advantages, but investors should not treat size as a guarantee of quality.

Larger funds may be able to execute trades more efficiently and spread rebalancing costs over a larger asset base. They can also have better liquidity and potentially tighter bid-ask spreads.

However, a large AUM does not automatically mean that a fund has a better tracking process. A fund can still have significant cash drag or inefficient rebalancing despite being large.

There is also another consideration. Some large funds may have substantial short-term institutional money. Sudden redemptions can force the fund to sell securities at inconvenient times, potentially increasing costs and tracking slippage.

Therefore, AUM should be treated as one factor rather than a quality score. Investors should first establish whether the fund has consistently tracked its benchmark well.

Is switching itself against passive investing?

Switching index funds is not necessarily inconsistent with passive investing. The key is why the investor is switching.

Passive investing means avoiding attempts to predict which stocks, sectors or market-entry points will outperform. Moving from one fund to another because the first fund persistently fails to replicate its benchmark is different from trying to time the market.

Shrivastava said switching because of structural issues, persistent tracking problems or a genuine long-term cost advantage can be prudent portfolio management.

What investors should avoid is switching because of a single weak quarter, a temporary rise in tracking error or the latest performance ranking.

For an investor holding an index fund for the long term, consistency of benchmark tracking is ultimately more important than chasing every small difference in returns, expense ratios or AUM.