Why the total expense ratio is only half the truth, and the tracking difference the more honest figure.
The TER states a fund's advertised running costs per year; the more honest figure is the tracking difference, the actual shortfall against the index over time. Through extra income such as securities lending it can come out smaller than the TER. Spread and order fees arise on top with every trade. Compare the tracking difference of several years first, then the TER.
The TER sits large on the factsheet, and many investors choose their ETF by it. Yet it measures only part of the costs, and not the decisive part. The more honest figure sits one line lower and is called the tracking difference.
Once you understand the cost mechanics, you compare ETFs differently: not by the advertised fee, but by what actually goes missing against the index.
The cheapest fee is worthless if the fund still trails its index. What counts is what arrives.
The TER (total expense ratio) bundles a fund's running costs: management fees, custodian fees, index licence costs, distribution and administration. It is stated as a percentage per year and is not debited separately; it is taken daily, pro rata, out of the fund's assets. You never see it as a charge, only as a slightly lower return.
What the TER does not contain, despite its name: the fund's own transaction costs when it rebalances, your order fees and spreads when you buy, and taxes at your level.
The tracking difference (TD) measures what is missing at the end: the gap between the index return and the fund's actual return over a period.
Tracking difference
TD = index return − fund return (per year)
A TD of 0.15% means the fund trailed its index by 0.15 percentage points per year. That is what you really paid, all fund costs and offsetting effects included.
Notably, the TD can be smaller than the TER, in some cases even negative. Funds earn extra income, from securities lending or from a more favourable withholding-tax treatment than the index assumes, and pass it on to investors. An ETF with a 0.20% TER and a 0.05% TD is in practice cheaper than an ETF with a 0.12% TER and a 0.18% TD.
| Figure | What it measures | Where it lives |
|---|
The TER (total expense ratio) bundles a fund's running costs: management, custodian, index licence and distribution. It is stated as a percentage per year and taken daily, pro rata, from the fund's assets rather than charged separately. It does not include the fund's transaction costs, your order fees and spreads, or taxes.
The tracking difference is the gap between the index return and the fund's actual return over a period. It measures what you really paid, all costs and offsetting income included. It can be smaller than the TER, for instance through securities-lending income, which makes it the more honest comparison figure.
Compare ETFs on the same index first by their tracking difference across several years; with similar TDs, the TER, fund size and tradability decide. Additionally mind the spread (trade liquid ETFs during main hours) and your broker's order fees, especially for small instalments.
| TER | Advertised running costs per year | Factsheet, KID |
| Tracking difference | Actual shortfall against the index | Provider reports, comparison portals |
| Spread | Buy/sell gap on the exchange | Order book, varies by time of day |
| Order fees | Your broker's charges | The broker's price list |
Two cost blocks arise not inside the fund but with you:
On top come taxes at your level: distributions, the Vorabpauschale (advance lump-sum tax) and gains on sale, softened by the 30% partial exemption for equity funds. They are not fund costs, but they belong in any honest net view.
Costs act like a negative return with compound interest. A difference of 0.3 percentage points per year sounds harmless, but over decades it adds up to several percent of final wealth. The ETF savings-plan calculator makes the effect visible if you run two return assumptions separated by the cost difference.
Compare ETFs on the same index first by their tracking difference across several years, not by the TER. With similar TDs, the TER, fund size and tradability decide.
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