How we calculate overlap

Updated September 11, 2026.

Overlap by weight

For two funds A and B, we normalise each fund's weights to 100% and sum the smaller of the two weights across every company both hold. That symmetric figure is the share of money that lands in the same companies — it is the same measure as 100 minus active share.

The Redundancy Score

The ETF Copilot Redundancy Score is the share of one fund's money that is already sitting inside another fund. It is directional, and the direction is the point: most of a focused fund can sit inside a broad one while only a sliver of the broad fund is the focused one, because the broad fund holds many times more companies. A single symmetric overlap number cannot say that, which is why we publish both directions.

Direction matters

Overlap has two directions that are usually not equal. 'A in B' is the share of A's weight that also sits in B; 'B in A' is the reverse. A small focused fund can be almost entirely inside a broad one while only a sliver of the broad fund is the small one. Reporting a single symmetric number hides which fund contains which — so we publish both.

How pairs are grouped

Each pair is placed into a relationship group by a fixed rule over the two directional figures — 'effectively the same fund' when both directions are very high, 'one sits inside the other' when there is a wide gap, and 'less alike than they look' when two same-category funds share little. The rule is the deliverable; if a pair looks miscategorised, the threshold is what to question, not the pair.

Aggregates only

We publish percentages, counts and ranks — never a constituent list. The overlap figures are derived aggregates; the underlying holdings and weights stay licensed.