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How to read a fund overlap report
Every comparison on OpenBell has five sections. Here's what each one tells you and how to use it.
Overlap Summary
The top section shows the headline overlap number and a bar chart for each fund.
The overlap percentage
OpenBell reports weighted overlap — the fraction of a fund's portfolio weight that is also held in the comparison fund. It is shown per fund because overlap is rarely symmetrical.
Example: If VOO shows 78% overlap with VTI, it means 78% of VOO's portfolio weight is in securities that VTI also holds. VTI might show only 45% overlap with VOO, because VTI holds many additional mid- and small-cap stocks that VOO doesn't — VOO's weight is almost entirely inside VTI, but the reverse isn't true.
The "weighted overlap" stat at the top is the average of both funds' overlap percentages. For a two-fund comparison, you can read each fund's bar directly to see the directional breakdown.
The overlap bars
Each bar shows one fund. The filled (accent-colored) portion is the overlap weight — the portion of that fund's portfolio that exists in the other fund. The unfilled portion is that fund's unique weight — positions not held in any other selected fund. A nearly full bar means the fund adds very little new exposure to your portfolio when combined with the others.
Shared Holdings
Every security held by two or more of the selected funds, sorted by average weight descending. This is where you see exactly which companies you're doubling up on.
Fund weight columns
Each fund has a column showing its weight in that security. A weight of 3.25% means 3.25% of that fund's total net assets are in this security. Where a fund doesn't hold the security, the cell shows — (for N-way comparisons where not every fund holds every shared security).
Avg % column
The average weight across all funds that hold this security. Useful for sorting: a security at 5% Avg is a more significant overlap than one at 0.01% Avg, even if technically both are "shared holdings."
Min weight filter
Large diversified funds can have thousands of holdings. Use the min weight filter (All / >0.1% / >0.5% / >1%) to focus on meaningful positions. A 0.005% weight in Apple is technically overlap, but it's not moving the needle on your portfolio's actual Apple exposure.
Unique Holdings
For each fund, this section lists holdings that no other selected fund holds — sorted by weight descending. This answers "what does this fund actually add to the portfolio that I don't already have?"
What to look for
If a fund's unique holdings are heavy at the top (large unique weights) — that fund is adding meaningful diversification. If its unique holdings are entirely sub-0.1% tail positions, the fund is essentially a more expensive version of the other funds in your comparison.
For thematic or sector ETFs compared against a total-market fund: the unique holdings often reveal the fund's actual thesis — e.g., a biotech ETF's unique holdings are almost entirely small-cap biotechs not in a total-market fund.
Overlap Concentration
This section breaks down the shared holdings by sector and country. It answers a different question: not just "how much overlap?" but "where is my overlap concentrated?"
Why this matters
Two funds can have moderate overall overlap but highly concentrated overlapping positions. For example: two large-cap funds that both heavily weight the Magnificent Seven tech stocks — their overlap is in the highest-conviction, most volatile names. That's different from two funds where shared holdings are spread across 40 sectors.
Sector and country data quality
Sector and country classifications come directly from NPORT-P filings, where funds report them for each holding. Not all funds report sector classifications, so the breakdown may be partial for some comparisons. The "uncategorized" bucket contains holdings where no classification was reported.
Data Sources
The footer shows the exact SEC filing behind each fund's data: the number of holdings in the filing, the date the holdings reflect (as of), the date the fund submitted the filing to EDGAR (filed), and a direct link to the filing itself.
As of vs. Filed
As of is the reporting period end date — the date the holdings reflect. A fund with "as of Dec 31" holds these securities as of the last trading day of Q4.
Filed is when the fund submitted the form to the SEC, typically 45–60 days after the period end. The SEC then makes it public shortly after. The "as of" date is what matters for understanding the data's freshness.
Putting it together: how to evaluate overlap
High overlap (>70%)
One fund is mostly inside the other. For passive index funds, this is expected — two S&P 500 funds will have 95%+ overlap. The question is whether you need both, or whether one is strictly better (lower expense ratio, more liquid, etc.). For active funds, high overlap may indicate "closet indexing" — the fund claims to be active but its portfolio looks like the benchmark.
Moderate overlap (30–70%)
The funds share significant ground but each adds some unique exposure. Whether this is "too much" depends on your intent. Holding VOO (S&P 500) and QQQ (Nasdaq 100) together is a deliberate tilt toward large-cap tech — you know what you're getting. Holding two large-cap value funds with 55% overlap might suggest you could simplify to one.
Low overlap (<30%)
The funds are genuinely diversifying relative to each other. A small-cap value fund vs. a developed-market international fund would typically show very low overlap. This doesn't mean they're uncorrelated — they can still move together in a market crash — but at the holdings level they're investing in different companies.
Try it now
Compare VTI vs VOO — a classic S&P 500 vs. total market comparison — to see what high overlap looks like. Or compare VTI vs IWM to see a total-market vs. small-cap comparison with meaningful differentiation.