Glossary › Index Overlap
Index Overlap
Share of a fund's AUM held in stocks that the benchmark also includes.
Formula
IndexOverlap(fund, index) = sum of fund's weight_pct for every fund-held stock that exists anywhere in the index
Intuition
If a fund has ₹100 of AUM and ₹85 of that sits in stocks the benchmark also contains (regardless of the benchmark's own weights), the number is 85%. It tells you whether the fund picks from the same stock universe as the benchmark.
What to look for
Not directly good/bad. Sectoral and international funds against a broad benchmark show low values (their stocks aren't in that benchmark). Active flexi-cap and large-cap funds against Nifty 500 routinely show 80-98% because Indian equities are dominated by large/mid caps that are all in Nifty 500 — that's universe coverage, not closet indexing.
Caveats
This is NOT the canonical 'min(fund_weight, index_weight)' portfolio overlap that distinguishes active management from closet indexing. To compute that we'd need each benchmark's per-stock weights, which we don't currently ingest. So a fund that holds the same 50 stocks as Nifty 500 but at completely different weights, and a fund that weights them exactly like Nifty 500, both score similarly here — only the latter is actually closet-indexing. Treat low values as a strong signal of off-benchmark exposure; treat high values as a weak signal.