Tracking error
Standard deviation of a fund's return minus its benchmark's return — measures how precisely an index fund replicates its benchmark.
Tracking error measures how closely an index fund, ETF, or passively managed scheme follows its designated benchmark. A zero tracking error would mean the fund replicates the benchmark perfectly; in practice, cash drag, rebalancing friction, and TER create a non-zero gap. For actively managed funds, tracking error measures how far the manager has departed from the benchmark — higher tracking error = more active positioning.
What it measures
Tracking error (TE) is the standard deviation of the active return series: the difference between the fund's monthly return and the benchmark's monthly return in each period. A large TE means the fund's returns diverge significantly from the benchmark in individual months — sometimes favourably, sometimes not. For an index fund, minimising TE is the primary objective. For an active fund, TE is an implicit measure of active risk taken.
How it is computed
active_return(t) = R_fund(t) − R_benchmark(t) for each month t
TE_monthly = σ(active_return series)
TE_annual = TE_monthly × √12
Where σ is the sample standard deviation. MintByte uses 36 months of monthly returns.
Example: Nifty 50 Index Fund — over 36 months, the monthly differences between fund and Nifty 50 had a standard deviation of 0.08%. Annualised TE = 0.08% × √12 = 0.28%. Excellent index replication.
Active mid-cap fund example: Monthly active return σ = 2.1%. Annualised TE = 7.3%. This fund takes substantial active bets relative to its benchmark.
How to interpret
For index funds / ETFs:
| Tracking Error | Quality |
|---|---|
| < 0.5% | Excellent replication |
| 0.5–1.0% | Good; check TER and trading costs |
| 1.0–2.0% | Moderate; investigate causes |
| > 2.0% | Poor for an index fund; significant cash drag or structural issue |
For active funds:
- TE 2–5%: Moderate active risk; manager is positioning meaningfully vs. benchmark but not drastically.
- TE 6–10%: High conviction active bets; can deliver high alpha or deep underperformance.
- TE > 10%: Very high active risk; benchmark comparison may be misleading.
Closet indexers (high-fee funds that barely deviate from the benchmark) often show TE of 1–2% despite charging active fees. A large-cap active fund with TE < 2% is effectively an expensive index fund — check alpha before paying the fee.
Limitations + caveats
Tracking error is a symmetric measure — it penalises both favourable and unfavourable deviations from the benchmark. A fund that consistently outperforms the benchmark will show non-zero TE despite positive outcomes. TE must therefore be read alongside alpha and capture ratios. For index funds, low TE is necessary but not sufficient — also check tracking difference (the mean of active returns, not just its dispersion), which captures the direction and magnitude of the systematic gap.
Related metrics
- Alpha — the mean of the active return series; tracking error is its standard deviation.
- Beta — for index funds, β close to 1.0 and low TE together confirm benchmark fidelity.
- Expense Ratio Drag — TER is the primary cause of non-zero tracking difference (mean active return) in index funds.
Sources
Monthly NAV and benchmark returns: AdvisorKhoj API. Benchmark assigned per SEBI category classification. Tracking error computed monthly over trailing 36 months (minimum 12 months); displayed on all index fund and ETF detail pages.