Read the last two columns together. Names that IWDA holds and VWCE does not make up 1.22% of IWDA’s weight, so by weight nearly everything in IWDA is also in VWCE. The reverse does not hold: VWCE’s 2,565 lines outside IWDA carry 14.99% of VWCE’s weight, and that side is what stops the overlap at 83.80%. SWRD follows the same pattern at 1.23% and 15.14%.

CSPX is the simplest case. On every one of the 442 shared securities, the lower weight is VWCE’s, so the 59.50% is VWCE’s own weight in the names CSPX holds. The 3,313 VWCE lines outside CSPX carry 39.70% of VWCE.

For scale, the MSCI World factsheet lists 1,280 constituents as of 31 Aug 2026; the IWDA file (as of 10 Sep 2026) has 1,251 lines and the SWRD file (as of 11 Sep 2026) has 1,239. iShares states the IWDA methodology as optimised in its August 2026 factsheet, and SSGA states SWRD’s replication method as optimised on its product page. The gap between 83.80% and 83.13% decomposes exactly into three parts:

Where the weight differences sit

Across the 1,234 names that both IWDA and SWRD hold, the median ratio of SWRD’s weight to IWDA’s is 1.00, so most names are weighted alike. The differences are concentrated in a tail:

• 67 names sit in SWRD at under half their IWDA weight. By country: 18 Japan, 7 Sweden, 6 Canada, 6 France, 3 each for the UK, Spain, Norway, Australia, Germany and Singapore, and single names for the rest. Only one of the 67 is a US name.
• Examples: Aker BP at 0.0015% in SWRD against 0.0135% in IWDA; Chiba Bank at 0.0003% against 0.0096%.
• 15 names sit in SWRD at over twice their IWDA weight.
• SWRD’s US weight is 71.38%, against 71.00% for IWDA.

Vanguard’s product page states that VWCE tracks its index using a representative sample. The VWCE holdings file as of 31 Jul 2026 has 3,755 equity lines. Vanguard’s factsheet for the same date lists 4,264 stocks in the benchmark. That is 509 fewer lines than the benchmark has constituents, or 88.1% held by count, with both figures on the same date.

The same factsheet reports 3,782 stocks in the fund. ETF Overlap Tool attributes the 27-line difference to its two line-count rules: lines with zero market value are excluded, and lines sharing an ISIN are merged into one (7 same-ISIN pairs, among them Royal Bank of Canada, Shopify and Ferrari). Vanguard no longer serves the 31 Jul 2026 holdings feed, so this cannot be reconciled line by line.

Top-ten concentration, step by step

Vanguard’s 31 Jul 2026 factsheet puts VWCE’s top ten at approximately 24.6% of net assets. Reading the same date’s holdings file gets there in two steps:

The route not taken, keeping share classes separate and then rescaling, gives 23.71%. The 24.60% route matches Vanguard’s factsheet figure. For reference, the top ten read from the other three files: IWDA 26.91%, SWRD 27.04%, CSPX 38.14%.

Matching securities

• Each holdings line is resolved to one canonical security, in this order: ISIN or CUSIP, with an alias table; then ticker plus listing currency; then normalised name plus currency, or country where that is unique; then name only, under refusal rules.
• No match in any of the three files comes from the name-only pass. IWDA has 6 matches from the normalised-name pass: STMicroelectronics, Bank of Ireland, ARC Resources, Kongsberg, CapitaLand Integrated Commercial Trust and CapitaLand Ascendas REIT. SWRD has 1 normalised-name match (Fresenius SE) and 1 ISIN-alias match (Wise).
• Each share class and each listing is a separate security. Alphabet A and C are two securities; Teva’s Tel Aviv line and its US ADR are two securities.
• Line-count rules: lines with zero market value are excluded, and lines sharing an ISIN are merged into one. Cash is excluded.

Weights

• Weights are never rescaled.
• VWCE: published percentages, as a percent of the full fund.
• IWDA and CSPX: derived from market value divided by net assets, because the published weight column is rounded to two decimal places.
• SWRD: published percentages, as a percent of the securities portfolio. SSGA lists cash and index futures without a percentage. ETF Overlap Tool confirmed this basis against the raw SSGA files on 2 Oct 2026: cash is 0.2 to 0.3% of SWRD’s net assets, so on a net-asset basis the VWCE vs SWRD overlap would be at most about 0.2pp lower.
• Weight overlap is the sum, over shared securities, of the lower of the two weights.

The addendum adjustment

The published CSVs read 83.78% overlap with 1,189 shared securities for VWCE vs IWDA, and 59.48% with 441 shared securities for VWCE vs CSPX. ETF Overlap Tool’s addendum of 17 Sep 2026 joins Vivmark Residential, which appears in the iShares files under its new name with no ISIN, to Equity Residential in the VWCE file (ISIN US29476L1070): Equity Residential and AvalonBay merged on 17 Aug 2026, with Equity Residential the surviving entity. This page uses the adjusted figures throughout.

Integrity checks

On every shared row, the overlap weight equals the lower of the two fund weights. No ISIN appears twice in any matched file.

No input on this page is modelled, so the test is against the matching and weighting choices instead: how share classes and listings are counted, whether names are joined at company level, and which weight basis each issuer uses. Each alternative is applied to all three pairs.

• Sampling is the first-order cause of unmatched names. Vanguard states that VWCE uses a representative sample. 12 names are unmatched against VWCE in all three other files, all of them US: Lumentum, Jabil, Tapestry, Casey’s, CF Industries, CH Robinson, Bunge, Nordson, Masco, EchoStar, Regency Centers and Lennox. The files cannot separate sampling from other causes.
• Porsche. Neither Porsche SE preference shares nor Porsche AG preference shares are in VWCE. Index methodology and sampling cannot be told apart from the files.
• AvalonBay. VWCE’s 31 Jul 2026 AvalonBay line (0.0248%) stays unmatched, because the September Vivmark line already includes that exposure. ETF Overlap Tool’s addendum treats this as a date effect, not an identifier mismatch.
• Weights printing as 0.0000%. Hologic (in IWDA and CSPX) and Nebius (in SWRD) print 0.0000% at four decimal places.
• IREN. IREN in IWDA (no ISIN) and Iris Energy in SWRD carry the same weight and are absent from VWCE in both cases. This is not a match failure.
• Weight bases differ by issuer. Percent of full fund for VWCE, market value over net assets for IWDA and CSPX, percent of securities portfolio for SWRD. See the fourth sensitivity row.
• As-of gap. VWCE’s holdings are a month-end file (31 Jul 2026); the other three are daily files from 10 and 11 Sep 2026.
• SWRD’s weight column sums to 100.0045%. ETF Overlap Tool’s addendum attributes this to print rounding.
• Holdings, not outcomes. Overlap by weight says nothing about returns, costs, tracking or tax. This study is educational and is not investment advice.

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