Tracking error measures how closely an ETF or investment fund follows the performance of its benchmark index over time. A lower tracking error generally means the fund tracks the index more consistently, while a higher tracking error means performance deviates more from the benchmark.
What Is Tracking Error?
Tracking error is a measure of the consistency of differences between an investment fund’s returns and the returns of its benchmark index over time.
In simple terms:
It shows how much an ETF “drifts away” from the index it is trying to track.
For example:
If the MSCI World Index rises by 10% over a year and an ETF tracking that index gains 9.8%, the ETF underperformed slightly.
Small differences are normal because ETFs have:
- Management fees
- Trading costs
- Rebalancing costs
- Tax effects
- Cash holdings
Tracking error measures how variable these differences are over time.
Tracking error is often calculated as the standard deviation of return differences between the ETF and its benchmark over time.
A low tracking error usually suggests:
- Efficient portfolio management
- Good replication quality
- Consistent benchmark exposure
A high tracking error may reflect replication challenges, market structure constraints, operational frictions, or portfolio-management limitations.
Tracking error is most relevant for:
- ETFs
- Index funds
- Passive investment strategies
It is less important for actively managed funds because active managers intentionally deviate from benchmarks.
How Does Tracking Error Work?
Here’s the simplified process step by step.
Step 1: The ETF Tracks an Index
An ETF selects a benchmark index such as:
- MSCI World
- S&P 500
- EURO STOXX 50
- Bloomberg Global Aggregate Bond Index
The goal is to mirror the index’s performance as closely as possible.
Step 2: Small Performance Differences Appear
Even passive ETFs cannot perfectly match an index at all times.
Differences can come from:
- Annual management fees
- Bid-ask spreads
- Transaction costs
- Taxes on dividends
- Cash drag
- Currency hedging costs
Index rebalancing schedules and portfolio turnover can also influence tracking behaviour.
Step 3: Performance Deviations Are Measured
Tracking error looks at how consistently the ETF’s returns differ from the benchmark over time.
If deviations remain small and stable, tracking error stays low.
If deviations become larger or more volatile, tracking error increases.
An ETF can have a small tracking difference but still experience higher tracking error if deviations fluctuate significantly over time.
Step 4: Investors Evaluate Replication Quality
Investors often compare ETFs tracking the same index by analysing:
- Tracking error
- Tracking difference
- Costs
- Liquidity
- Replication method
Lower tracking error is generally preferred for passive investing because it suggests the ETF is behaving similarly to the benchmark.
Example of Tracking Error
Imagine two European UCITS ETFs both track the MSCI Emerging Markets Index.
Over one year:
- ETF A returns 7.9%
- ETF B returns 7.2%
- The benchmark index returns 8.0%
ETF A stayed relatively close to the benchmark throughout the year.
ETF B experienced larger fluctuations and deviations during periods of market volatility.
As a result:
- ETF A likely had lower tracking error
- ETF B likely had higher tracking error
Even if two ETFs track the same index, their tracking quality can differ because of:
- Replication method
- Portfolio management
- Trading efficiency
- Securities lending
- Fund costs
Pros and Cons of Low Tracking Error
Pros
- Closer benchmark replication
- More predictable index exposure
- Usually preferred for passive investing
- Can indicate efficient portfolio management
- Helps investors compare similar ETFs
Cons
- Very low tracking error does not guarantee higher returns
- Some specialised markets naturally produce higher tracking error
- Bond and emerging-market ETFs may face replication difficulties
- Tracking error can change during market stress
- Lower-cost ETFs do not always have lower tracking error
What Causes Tracking Error?
Several factors can influence tracking error.
Common causes include:
- Management fees
- Sampling techniques
- Rebalancing delays
- Illiquid securities
- Currency hedging
- Dividend withholding taxes
- Cash holdings
- Trading spreads
- Market volatility
Bond ETFs often experience higher tracking error because bond markets can be less liquid and less transparent than equity markets.
Synthetic ETFs can sometimes achieve lower tracking error than physical ETFs because swap agreements may replicate benchmark returns more precisely in certain markets.
However, results depend on market conditions and ETF structure.
Securities-lending revenue may sometimes reduce tracking difference, although results vary between funds.
European Context
Tracking error is particularly important in Europe because the European ETF market includes many:
- UCITS ETFs
- Cross-border funds
- Currency-hedged ETFs
- Bond ETFs
- Synthetic ETFs
European investors frequently compare ETFs listed across:
- Xetra
- Euronext
- London Stock Exchange
- SIX Swiss Exchange
Although multiple ETFs may track the same benchmark, tracking quality can still vary significantly.
European UCITS regulations require ETF providers to disclose detailed information about:
- Replication methods
- Costs
- Risks
- Portfolio composition
This information is usually available in:
- Key Information Documents (KIDs)
- Factsheets
- Prospectuses
European investors should also understand that:
- Currency hedging can influence tracking error
- Withholding taxes may affect international equity ETFs
- Bond-market liquidity can affect fixed-income ETFs
- Securities lending revenue may partially offset ETF costs
Two ETFs tracking the same index may still produce different tracking errors depending on methodology, implementation, and operational efficiency.
Major European ETF providers commonly publish tracking statistics directly on their websites.
Related Concepts
- Tracking Difference — The difference between an ETF’s actual return and the benchmark’s return over a specific period
- Full Replication — A strategy where an ETF owns all securities inside the benchmark index
- Sampling — A replication technique using a representative subset of index securities
- Synthetic Replication — A method using derivatives such as swaps to track an index
- UCITS ETF — A European-regulated ETF structure designed for retail investors
FAQ
Tracking error measures how closely an ETF or index fund follows its benchmark index over time. A lower tracking error generally means the fund is tracking the index more consistently.
Tracking error can be caused by management fees, trading costs, taxes, rebalancing delays, cash holdings, currency hedging, and liquidity issues. Market volatility can also increase tracking deviations.
In most passive investing strategies, lower tracking error is generally preferred because it means the ETF behaves more similarly to its benchmark index. However, low tracking error alone does not guarantee better returns.
Tracking difference measures the actual performance gap between an ETF and its benchmark over a period of time. Tracking error measures how consistently that gap changes over time.
Synthetic ETFs can sometimes achieve lower tracking error than physically replicated ETFs because swap agreements may replicate benchmark returns more precisely. However, results depend on market conditions, costs, and ETF structure.
This content is for general educational purposes only and does not constitute investment, tax, or legal advice. Investment outcomes and tax treatment depend on individual circumstances and country-specific rules.
Sources
- European Securities and Markets Authority – MiFID II investor-protection rules, fund disclosure standards, and best execution requirements in EU financial markets
- European Commission – UCITS framework, PRIIPs regulation, and Key Information Document (KID) requirements for retail investment products in the European Union
- European Central Bank – Interest rates, inflation, and long-term effects of costs and compounding on investment outcomes
- CFA Institute – Investment fund costs, portfolio construction, passive investing, and long-term investing principles
- Academic finance research (various journals) – Evidence on fund expenses, compounding effects, active vs passive investing, tracking difference, and long-term investor returns
- ETF issuer educational materials (various providers) – Information on accumulating vs distributing ETFs, UCITS fund structures, synthetic replication methods, and ETF domicile considerations
Iva Buće is a Master of Economics specializing in digital marketing and logistics. She combines analytical thinking with creativity to make financial and investment topics accessible to a broader audience. At Finorum, she focuses on translating complex economic concepts into clear, practical insights for everyday readers and investors.
Sources & References
EU regulations & taxation
- European Commission / Taxation & Customs — Interest rates, inflation, and long-term effects of costs and compounding on investment outcomes
- MiFID II investor-protection rules, fund disclosure standards, and best execution requirements in EU financial markets
- UCITS framework, PRIIPs regulation, and Key Information Document (KID) requirements for retail investment products in the European Union