The top ten is the book.
A family office book is short, and the money inside it is shorter still. The names below the tenth line are, in aggregate, a rounding error on the ones above it.
89%
of the reported listed book sits in the ten largest names, in the middle office of the newest quarter on file. In the most concentrated quarter of them it is 100%.
How concentrated is a family office, really?
Concentration is not the tail of this distribution. It is the whole of it. Even the least concentrated tenth of these offices keep the bulk of their reported money in ten lines.
| Money in the ten largest names | Lowest tenth | Lower quarter | Middle | Upper quarter | Highest tenth |
|---|---|---|---|---|---|
| Top ten weight | 51% | 66% | 89% | 100% | 100% |
Read the other way round: the handful of positions that carry the book hold 82% of the money in the middle office. The question a committee should be asking was never how many names are on the list. It is which few are on it, and why.
Whose concentration is it — yours, or everyone’s?
There is a second kind of concentration, and it does not appear on any allocation report: the names you hold that everyone like you also holds. When those positions are sold, they are often sold by many people in the same week.
In this cohort the middle office already owns 4% of what the rest of them own. The crowded tenth sit at 15%. Diversifying into the same crowd is not diversifying.
What should you check in yours?
- The share of the listed book in the ten largest names, and whether it moved because you decided or because the market did.
- Which positions fall together. A group that shares one downside is one position wearing several names.
- Where the risk sits against where the money sits. A line can be four percent of the money and a fifth of the risk.
- What a forced sale would have to touch, if the quarter went badly and a capital call arrived anyway.
What these percentages cannot tell you.
- Only listed shares held long are reported. Private funds, direct deals, property, cash, debt, fees and tax are all outside the filing.
- A filing is a photograph of one day, published up to 45 days later. It cannot show what was bought and sold in between.
- Only offices above the reporting threshold appear at all, so the cohort skews larger than the category.
- No prices are licensed here, so nothing in this cohort is a return, a ranking, or a backtest. Holdings facts only.
- Weights are struck on the filing date. A concentrated book can be the result of one position rising, not of anyone buying.
- Crowding is measured inside this cohort only. It says how much these offices look like each other, not how much they look like the market.
How the cohort was assembled.
A screen proposed 51 filers as candidate family offices. A person read every one: 40 were accepted, 7 were rejected as something else, and 4 were left open because the evidence did not settle it. Only the accepted ones are in any figure on this page.
That is 874 filings and 61,471 reported positions across 22 quarters, each one read as of the day it became public rather than with the benefit of hindsight. A filing that arrived late is missing from its quarter instead of being back-filled into it.
The cohort is other firms' public quarterly filings, read as they stood on the day each one became public. It is not our clients, not their data, and not a performance record. Counts as at 19 September 2026.
Public filings only, and only the part of a book they cover: listed shares held long. No private holdings, no cash, no debt, no fees, no tax. Offices that stopped filing stay in every figure. Nobody here is named. Figures above are computed from the filings themselves, as they stood on 2026-09-20. A record and an analysis, not investment, tax or legal advice; decisions rest with the family and its advisers.