Can a Fund's Tracking Difference Ever Be Positive?
It seems like a fund tracking an index should, at best, match it and, more realistically, trail it slightly because of fees — yet every so often a fund’s return actually comes out ahead.
The short answer
Yes, a fund’s tracking difference can be positive, meaning its return slightly exceeds its benchmark’s return over a given period, net of fees. This is less common than a fund trailing its index, but it happens, usually because of extra income sources like securities lending, favorable sampling or trading decisions, or timing effects that occasionally work in the fund’s favor rather than against it.
Why this seems counterintuitive at first
A fund carries costs an index doesn’t — an expense ratio, trading costs, and sometimes cash drag — so intuitively its return should always land a bit below the theoretical index. Most of the time, that intuition holds and tracking difference is negative or close to zero. But an index is a theoretical calculation with no trading costs of its own, while a fund is a living portfolio that can occasionally generate extra income or benefit from favorable timing that outweighs its costs in a given stretch.
The most common sources of positive tracking difference
- Securities lending income. When a fund earns meaningful income from lending out its holdings, that revenue can occasionally exceed the fund’s expense ratio and other costs for a period, pushing the net return slightly above the benchmark.
- Favorable sampling outcomes. A fund using sampling instead of full replication might, by chance or by the manager’s construction choices, hold a set of securities that outperforms the full index slightly during a specific period.
- Trading efficiency. Skilled execution around index rebalancing dates can sometimes reduce trading costs below what a naive full-replication approach would incur.
- Timing quirks. For international funds, pricing-related adjustments made after a foreign market closes can occasionally work in the fund’s favor for a given day or period, though this tends to be temporary and can reverse just as quickly.
Why this shouldn’t be read as a promise
A single period of positive tracking difference doesn’t mean a fund will consistently beat its index going forward, and it’s not a sign that the fund is doing something exotic or unusually clever. Most of these effects are modest, and a fund that has costs will typically still average some drag over long periods, even if certain years or quarters look positive. It also doesn’t necessarily reflect anything about the broader market’s direction — a fund can post a positive tracking difference in a year when the index itself was flat or even down.
What to weigh
Occasional positive tracking difference is a real, documented possibility rather than a reporting error, and it usually traces back to identifiable sources like lending income or sampling outcomes rather than the index itself moving. Looking at a fund’s tracking difference across multiple periods, rather than one especially favorable stretch, gives a more balanced sense of how it’s likely to behave on average and helps separate a genuine pattern from an isolated coincidence.