ETF Tracking Error: Is Your Index Fund Lying?

Not all ETFs perfectly copy their index. Tracking error measures how much your ETF drifts from its benchmark. A high tracking error means you're paying for index returns but getting something worse. Here's how to check before you invest.

Here's what happened: Tracking error measures how consistently an ETF mirrors its benchmark index — it is the standard deviation of monthly return differences between the ETF and its index.. A high tracking error means your ETF swings away from the index unpredictably, even if the average annual gap looks small on paper.. Indian sectoral and mid-cap ETFs often show tracking errors of 1–2.5% annually, while large-cap Nifty 50 ETFs from major AMCs typically stay below 0.5%..

What you should do: Check both tracking error AND tracking difference for any ETF you hold or plan to buy — use AMC factsheets or screeners updated monthly.. Compare at least 3 ETFs tracking the same index before investing — choose the one with the lowest tracking error AND lowest expense ratio combined.. Avoid ETFs with low AUM (below ₹500 crore) since thin liquidity worsens tracking error through wider bid-ask spreads and cash drag..

Tracking difference (annual total return gap vs index) is more actionable than tracking error alone — an ETF can be consistent but still consistently underperform. Always check both numbers.

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