Definition
Fund overlap is the duplication created when two or more funds hold the same securities. Hidden concentration can also arise when different holdings respond to the same sector, factor, country, or underlying company.
Overlap can be measured as shared holdings, shared portfolio weight, or the minimum of each shared position's weight. No single percentage captures every form of common risk.
Why It Matters
Owning ten ETFs is not the same as owning ten independent strategies. Broad-market, growth, and technology funds may all place large weights in the same companies. Income ETFs tied to one stock can compound exposure already held through an index fund or direct shares.
Example
A portfolio invests 50% in Fund A and 50% in Fund B. Both allocate 12% to the same company. The portfolio's company exposure is 50% × 12% + 50% × 12%, or 12%, not 6%. Fund labels did not reduce the underlying concentration.
Common Mistakes
- Counting ticker symbols instead of underlying exposures.
- Checking only the top ten holdings.
- Ignoring sector, factor, issuer, and options-underlying concentration.
- Assuming a low historical correlation will remain low in a crisis.
FAQ
Is overlap always bad?
No. Intentional overlap can tilt a portfolio toward a desired company or factor. The problem is unmeasured overlap that exceeds the investor's risk limit.
How often should holdings be checked?
At least during a scheduled portfolio review and after a fund changes its index or strategy. Published holdings and weights can change between reviews.
