How WhaleCreep reads 13F filings
Every number on this site is computed from the managers' own Form 13F filings, fetched from SEC EDGAR, and nothing is estimated from anywhere else. This page explains what is measured, what is deliberately not, and the three data problems that have to be solved before any 13F figure can be trusted.
What a 13F is
Form 13F is a quarterly report that institutional investment managers with at least $100 million in US equity assets must file with the SEC within 45 days of each calendar quarter-end. It lists long positions in US-listed equities and certain options at their quarter-end value. It does not include short positions, swaps or most derivatives, cash, leverage, or non-US holdings.
What is measured, and what is not
- Holdings and weights. Each position as a share of the manager's reported equity book. Options are reported at underlying notional and excluded from the equity book by default.
- Changes in shares, not value. Value moves with price, so a book that did nothing shows bigger numbers after a rally. Comparing share counts isolates the manager's actual decision. A change is only computed against the immediately preceding filing; a gap of more than one quarter voids the comparison.
- Concentration. Largest position, top-ten weight, and effective positions (1/HHI: the number of equal-weight positions the book behaves like). Reported for the latest quarter and as a median across every quarter filed, so one unusual quarter neither qualifies nor disqualifies a manager. The concentration gate is a median largest position of 5%.
- Holding tenure. Completed holding spells only. Positions still open have an unknown final length and are reported separately as lower bounds, because pooling them understates exactly the long-held conviction names.
- Crowding. Names held by many managers at a meaningful weight of their own book, and, more usefully, names several managers opened in the same quarter.
- Not performance. A 13F is long-only US equity with no shorts, derivatives, leverage, cash or international, so a manager's real return cannot be derived from it. WhaleCreep does not publish 13F-derived "returns" and does not rank managers by them.
Three things that are wrong in raw 13F data
1. The value column changed units
Form 13F's value field was denominated in thousands of dollars before the 2023 amendment and in whole dollars after, and filers switched on their own schedules. Applying one rule to the whole history produces a set that is right for some fund-quarters and wrong by exactly 1000× for others. WhaleCreep detects the units per filing by arithmetic: value divided by shares is an implied share price, and its median across a filing must land where real equities trade. The original value and the divisor applied are both kept, so every correction is auditable.
2. Amendments come in two kinds
A 13F-HR/A can either add positions omitted from the original or restate the whole table. Summing every accession double-counts restatements; keeping only the newest discards a full original in favour of a one-row addition. Each amendment is classified by how much its CUSIP list overlaps what is already on file, and one effective book is kept per quarter.
3. Issuer names do not resolve to tickers
13F issuer fields are abbreviated and truncated. Positions are mapped to tickers on CUSIP, the identifier the filing actually gives, via OpenFIGI, restricted to US listings so a foreign line cannot win over the US listing the filing refers to. Sectors then come from the ticker.
How the manager list is built
The universe is seeded from public reputation and manager lineage across seven styles: Tiger lineage, activist, concentrated value, quality compounders, macro and discretionary, permanent capital, and emerging concentrated managers. Where a public ranking supports a name, the source and edition are recorded. Long-run outperformance is treated as a claim, never as a measurement; concentration is measured directly from the filings and is what the site's rankings use. A few deliberately diversified quant books are included as a control that the concentration metric works.
Freshness
EDGAR is checked every day. A 13F describes holdings as of quarter-end and is filed up to 45 days later, so the newest filing is between 45 and 135 days old at any moment. Every page states the quarter its figures describe and the date the filing was made.
Questions
What is a 13F filing?
Form 13F is a quarterly report that institutional investment managers with at least $100 million in US equity assets must file with the SEC within 45 days of each calendar quarter-end. It lists their long positions in US-listed equities and certain options. It does not include short positions, most derivatives, cash, or non-US holdings.
How current is 13F data?
A 13F describes holdings as of the quarter-end and is filed up to 45 days later, so the newest filing is between 45 and 135 days old at any given moment. WhaleCreep checks EDGAR every day and shows the date each filing was made.
Can 13F filings tell you a hedge fund's performance?
No. A 13F is long-only US equity with no shorts, derivatives, leverage, cash or international positions, so a fund's real return cannot be derived from it. WhaleCreep measures concentration and holding tenure, which a 13F does support, and never presents long-book replication as performance.
Why do position changes use share counts rather than dollar values?
Dollar value moves with the share price, so a book that did nothing shows bigger numbers after a rally. Comparing share counts isolates the manager's actual decision to buy, hold, trim or sell.
What does 'effective positions' mean?
It is the reciprocal of the Herfindahl index of portfolio weights: the number of equal-weight positions the book behaves like. A manager with six real bets and ninety tiny positions has ninety-six holdings and an effective count near six.