Read the full benchmark name
A stock is a share of ownership in a company. A stock index combines the price movements of a selected group of companies into one measure. A fund can aim to follow that measure, its benchmark. Two funds investing in the same country's large companies need not follow the same benchmark: they may put different proportions of the money in each company.
Take an invented index with just two stocks. Over one period, A rises 10% and B falls 10%. Put 80% of the starting money in A and 20% in B and the result is 0.8 × 10% + 0.2 × (−10%) = 6%. Put half in each and the result is 0%. This assumes no changes to those starting proportions, no dividends and no costs. The six-percentage-point gap comes entirely from how the money was divided.
A fund's weight in a company means that company's share of the money. One index gives the largest companies the largest weights; another gives every company an equal weight. The same names can therefore produce different returns. Read the full benchmark name rather than relying on a broad market label.
Even funds following the same benchmark can take different routes. One may buy every investment in it, while another buys a sample intended to move similarly. A fund may also use derivatives, contracts whose value depends on another investment or index. Then the other parties' ability to honour the contracts and the assets set aside as collateral matter too. A matching objective does not make the holdings and risks identical.
Also match the benchmark's currency and whether it includes dividends, the cash companies pay shareholders. A fund aiming for a multiple of each day's return, or the opposite return, has a different objective. Our daily 2x ETF example shows why a flat index over two days can still leave that fund with a loss.
Separate annual fund expenses from the cost of a trade
Running a fund costs money. Suppose A's annual expense rate is 0.10% and B's is 0.30%. If the value used to calculate each fund's expenses averages $10,000 over the year, the simple cost equivalents are $10 and $30: a $20 difference. Actual charges depend on changing asset values and each fund's calculation method.
Read what the percentages cover before comparing them. One management fee is not necessarily the full recurring expense figure. Expenses taken from the fund are also separate from fees you pay a broker, the intermediary that handles your trade.
Trading has another cost. Sellers quote a price at which they will sell, called the ask; buyers quote a price at which they will buy, called the bid. The gap is the bid–ask spread. The following separate example buys one share at the ask and immediately sells at the bid. Quotes stay unchanged, enough shares are available, and there is no commission or tax.
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| Fund | Price to buy | Price to sell | Difference | Loss on purchase price |
|---|---|---|---|---|
| ETF A | $100.10 | $99.90 | $0.20 | About 0.20% |
| ETF B | $100.50 | $99.50 | $1.00 | About 1.00% |
For A, divide the $0.20 loss by the $100.10 purchase price; for B, divide $1 by $100.50. That is about 0.20% and 1.00%. Buying alone has not locked in the full round-trip loss, and actual quotes and quantities change. The example shows why low annual expenses do not necessarily mean a low cost for buying and selling.
A tight spread also leaves a different question: how does the traded price compare with what is inside the fund? Net asset value, or NAV, is the fund's assets minus what it owes, divided among its shares. A market price above NAV is a premium. Bid and ask can be close together while both are above NAV. A narrow gap between the quotes does not establish that either is close to the value of the holdings.
Paying in your home currency does not remove currency exposure
A fund's documents may name a trading currency, a currency for reporting its accounts, and the currencies of its underlying investments. These need not be the same. A quote in your home currency is not evidence that foreign-currency risk has been hedged.
Imagine an unhedged holding worth US$100. One dollar initially costs 1.25 units of your home currency, so the holding is worth 125 local units. The asset rises 8% to US$108, while the price of one dollar falls 10% to 1.125 local units. You now have 108 × 1.125 = 121.5 local units: a 2.8% loss in home-currency terms.
With no income or costs, the combined return is (1 + 8%) × (1 − 10%) − 1 = −2.8%. Simply subtracting 10% from 8% misses the multiplication.
A currency hedge is a separate arrangement intended to reduce specified exchange-rate effects. Check which currency movements the hedge covers and how much of the exposure it is intended to offset. Hedges can cost money and may leave some exchange-rate risk uncovered. They do not protect against every decline in the underlying investments.
Keep the exact product and share-class identifiers beside your notes. A share class is a version of a fund with its own terms, such as fees or how income is paid. Similar names can hide differences in fees or distribution policy. A class that pays cash and a class that retains income need a total-return comparison; price charts alone leave out the cash paid by the distributing class. For hedging, use the policy of the actual product being compared.
Tracking difference and tracking error measure different things
After checking what the fund holds and costs, you can ask how closely it followed its benchmark. Suppose the index returns 8.0% over a year and the ETF's NAV total return is 7.7%. Total return includes the cash paid out as distributions. Here both figures assume that cash was reinvested, and use the same period and currency.
Using fund return minus index return gives −0.3 percentage points. This gap is the tracking difference: the fund finished that far behind the index. It is not an extra fee charged to your account. Expenses, holding only a sample of the index, keeping cash and trading at different times can all contribute. Expenses already included in the return should not be deducted again.
Tracking error asks how much that fund-minus-index return varies across measurement periods. A fund staying slightly behind and a fund swinging from ahead to well behind may have the same year-end gap. Their routes were different. Before comparing published tracking-error numbers, check the provider's definition, how often it measured returns and how it converted the result to a yearly basis.
These figures describe the fund's performance. Your own return can differ because you bought and sold at market prices and paid your own transaction costs.
Put the assumptions beside each return
Keep the exact product and share-class identifiers in your notes. A share class is a version of a fund with its own terms, such as fees or how it pays income. Add the full benchmark name, how the fund follows it and its currency-hedging policy, which says what exchange-rate effects it aims to reduce.
For performance, match dates, currency and the treatment of distributions. A price chart for a fund paying out cash leaves out that cash; a total-return figure includes it. Then check what each expense figure covers and when the trading quotes and NAV comparison were measured. Without those conditions, a higher return may be answering a different question.
A $10 share is not automatically better value than a $100 share. Comparable collections of investments can simply be divided into different-sized units. The lower share price does not mean the same money buys more underlying assets. Even with all conditions matched, a past return gap does not promise the same gap next time. These checks help explain what happened.
About the examples
All prices, fees, weights, exchange rates and returns in the examples are invented. The spread example assumes an immediate round trip at unchanged quotes with enough shares available. Match each example’s stated currency, period, distribution and cost assumptions; none of the figures is a quote or forecast. Editorial policy.