Tracking difference and tracking error are important metrics in index funds as they indicate how closely a fund has tracked its benchmark index. While tracking error measures the consistency of deviations between the fund and the benchmark, tracking difference measures the difference in returns generated by the fund compared to the benchmark. Together, these metrics may help investors assess how closely an index fund has replicated its underlying index.
Table of Contents
What is a tracking error?
Tracking error measures the extent to which an index fund’s returns deviate from its benchmark over a period of time. It is typically calculated as the standard deviation of the difference between the fund’s returns and the benchmark’s returns. Tracking error reflects the consistency of deviations from the benchmark. A lower tracking error generally indicates that the fund has tracked the benchmark relatively closely over time.
What is a tracking difference?
Tracking difference refers to the difference between the returns delivered by an index fund and the returns of its benchmark over a specified period. It is generally disclosed across periods such as 1 year, 3 years, 5 years, 10 years and since inception.
For example, if a benchmark generates 12% returns over 3 years and the index fund delivers 11.5% during the same period, the tracking difference would be -0.5%. This reflects the extent to which the fund underperformed or outperformed the benchmark during that period.
Tracking difference is often negative because expenses, transaction costs and cash holdings may reduce returns relative to the benchmark.
The figures shown are for illustrative purpose only
Tracking difference vs tracking error: Key differences
While both metrics measure how closely an index fund follows its benchmark, they capture different aspects of tracking performance:
| Feature | Tracking difference | Tracking error |
| What it measures | Difference between the fund’s return and the benchmark’s return | Consistency of deviations between the fund and benchmark returns |
| Focus | Return gap | Variability of the return gap |
| Expressed as | Percentage difference in returns | Standard deviation of return differences |
| Time period | Measured over a specific period | Measured across multiple observations over time |
| What it indicates | How much the fund has underperformed or outperformed the benchmark historically | How consistently the fund has tracked the benchmark |
| Lower value generally suggests | Returns have historically been closer to the benchmark | More consistent benchmark tracking |
| Key drivers | Expense ratio, transaction costs, cash holdings and rebalancing | Portfolio management, rebalancing and replication efficiency |
How is each metric calculated and interpreted?
Tracking difference and tracking error both help measure how closely an index fund has tracked its benchmark, but they focus on different aspects of performance.
Think of the benchmark index as a reference point that the index fund aims to follow as closely as possible. Tracking difference measures the overall gap between the fund’s returns and the benchmark’s returns over a specific period, while tracking error measures how consistently the fund has tracked the benchmark over time.
Tracking difference is calculated by comparing the fund’s return with the benchmark’s return over a given period. For example, if a benchmark delivers a return of 14% over one year and the index fund generates 13.6%, the tracking difference would be -0.4%.
The closer the tracking difference is to zero, the closer the fund’s returns have historically been to those of the benchmark.
Tracking error measures the consistency of these return differences over time. For example, two funds may both end the year with a tracking difference of -0.4%, but one fund may have stayed relatively close to the benchmark throughout the year while the other experienced larger deviations before ending at the same point.
Technically, tracking error is calculated as the annualised standard deviation of the difference between the fund’s returns and the benchmark’s returns. For most investors, it can be viewed as a measure of how consistently a fund has tracked its benchmark historically.
A lower tracking error generally indicates relatively more consistent benchmark tracking, while a higher tracking error may indicate greater variation in benchmark tracking over time.
The figures shown are for illustrative purpose only
Why do both metrics matter for index fund investors?
Tracking difference and tracking error provide different insights into how closely an index fund has followed its benchmark over time.
Tracking difference helps investors understand the overall gap between the fund’s returns and the benchmark’s returns over a specific period. Tracking error, on the other hand, helps explain how consistently the fund has tracked the benchmark during that period.
Looking at both metrics together can provide a more complete picture of a fund’s benchmark-tracking efficiency. For example, two funds may have a similar tracking difference, but one may have tracked the benchmark more consistently than the other.
Comparing these metrics across funds tracking the same benchmark may help investors understand how closely different index funds have historically followed their benchmark. Even relatively small differences can add up over longer periods. As a result, a fund that consistently deviates from its benchmark may deliver returns that differ from the benchmark over time.
What are acceptable values for each metric in India?
SEBI has prescribed tracking-related norms for passive funds to help ensure transparency in benchmark tracking.
For equity ETFs and equity index funds, SEBI requires tracking error to be monitored using one-year rolling data and has prescribed a limit of 2%, subject to certain exceptions in unavoidable circumstances.
For debt ETFs and debt index funds, SEBI has prescribed that the annualised tracking difference averaged over a one-year period should not exceed 1.25%.
Investors can review tracking error and tracking difference disclosures available in scheme-related documents, AMC disclosures and AMFI data to understand how closely a passive fund has tracked its benchmark historically.
Source: Securities and Exchange Board of India (SEBI), Master Circular for Mutual Funds, March 2026.
Why do tracking metrics matter in index funds?
Understanding tracking metrics can help investors gain a clearer picture of how closely an index fund has followed its benchmark over time:
- Even relatively small differences between a fund’s returns and its benchmark’s returns may add up over longer investment periods.
- Tracking metrics can help investors understand whether a fund has historically delivered returns that were relatively close to its benchmark.
- Persistent deviations from the benchmark may affect how closely a fund’s performance reflects the performance of the underlying index.
- Factors such as expense ratios, transaction costs, cash holdings and portfolio rebalancing may contribute to tracking differences and tracking errors.
- Looking beyond past returns and reviewing tracking metrics may provide additional insight into a fund’s benchmark-tracking efficiency.
- Reviewing tracking metrics alongside scheme-related documents can help investors develop a broader understanding of a fund’s characteristics and risks.
How to use both metrics when evaluating index funds
Tracking difference and tracking error may be useful when comparing index funds that track the same benchmark. For example, a Nifty 50 index fund is generally compared with another fund tracking the Nifty 50 Index rather than a different index.
Tracking difference, tracking error and expense ratios may provide useful context when assessing how closely a fund has historically tracked its benchmark.
Understanding tracking difference
Tracking difference reflects the gap between a fund’s returns and the returns of its benchmark over a specific period. Reviewing this metric may help investors understand how closely the fund’s historical returns have aligned with the benchmark.
Understanding tracking error
Tracking error reflects the consistency of deviations between the fund and the benchmark over time. This metric may provide insight into how consistently the fund has historically tracked the benchmark.
Comparing similar funds
Tracking metrics are generally most meaningful when comparing funds that track the same benchmark. For example, a Nifty Next 50 index fund would typically be compared with another Nifty Next 50 index fund rather than a fund tracking a different index.
Conclusion
Tracking difference and tracking error can help investors understand how closely an index fund has historically followed its benchmark. While tracking difference shows the gap between the fund’s returns and the benchmark’s returns, tracking error indicates how consistently the fund has tracked the benchmark over time.
Along with factors such as expense ratios, portfolio characteristics and scheme-related information, these metrics can provide useful insights when evaluating an index fund. However, investors should read all scheme-related documents carefully and consider their risk appetite, financial goals and investment horizon before making investment decisions.
FAQs
Which is more important: tracking error or tracking difference?
Both tracking error and tracking difference are important because they measure different aspects of benchmark tracking. Tracking difference shows the return gap between the fund and the benchmark, while tracking error shows how consistently the fund has tracked the benchmark over time.
Does tracking error affect my actual returns?
Tracking error does not directly measure return loss. However, higher tracking error may indicate greater variation between the fund’s returns and the benchmark’s returns over time.
Which index fund in India has the lowest tracking difference?
Tracking difference varies across index funds and may change over time. Investors can refer to AMFI disclosures, scheme factsheets and AMC websites to compare tracking differences across funds tracking the same benchmark.
What is a good tracking error for a Nifty 50 index fund?
For equity index funds such as Nifty 50 index funds, SEBI has prescribed that tracking error should not exceed 2%, subject to certain exceptions. A relatively lower tracking error generally indicates more consistent benchmark tracking.
How does an expense ratio affect tracking difference?
Expense ratio is one of the costs that may reduce a fund’s returns compared to its benchmark. As a result, it may contribute to a negative tracking difference over time.
