• Crowded hedge fund positions started falling two weeks before the November 5 sell-off. Momentum stocks held by many hedge funds in small positions fell 10% into October 22 while the S&P 500 fell 1%. In the two weeks that followed they fell another 11%, against 4% for the index.

• The crowded momentum winners gave back the year. The momentum names held by many hedge funds in small positions peaked up 43% in June and were up 6% at the November 6 close. The names held by fewer funds in bigger positions were up 19%.

• The crowded names fell together in every kind of hedge fund’s book. From October 23 to November 6 they fell 11 to 13% in all nine S3 style cohorts, while each cohort’s other momentum stocks ranged from down 12% to up 2%.

The Crowded Basket Broke Two Weeks Early

From September 1 the crowded momentum names ran ahead of the S&P 500. In the ten trading days to October 22 they fell 10% while the index fell 1%. That is what the start of an unwind looks like in this data. November 5 was the worst day of the move, not the start of it: by November 6 the crowded names were down 20% over four weeks against 6% for the index, the widest four-week gap in eleven years of S3 data.

Crowded vs Conviction Momentum Winners

S3 tracks hedge fund long positions stock by stock and classifies the funds by style. We took the US stocks with the best returns over the past twelve months and sorted them by stake per fund, the average hedge fund position in each. The top fifth are conviction: about 35 funds owning 12% or more of the company between them. The bottom fifth are crowded: about 90 funds owning 8% or less. Crowded does not mean hedge funds own a lot of a stock. It means many of them own a little. The crowded group peaked up 43% in early June and was up 6% at the November 6 close. The conviction group was up 19%, the S&P 500 up 8%.

Crowded Names Fell Across Hedge Fund Style Cohorts

S3 sorts hedge funds into nine style cohorts. Several hold only 13 to 53 of the 81 crowded names. From October 23 through November 6, the crowded momentum names in every cohort’s book fell 11 to 13%. The rest of each cohort’s momentum stocks went their own way, from down 12% at energy funds to up 2% at healthcare funds. Whatever kind of fund you ran, your crowded winners fell: the stocks stopped trading on their own news and started trading on who owns them.

On size and sector: the crowded names are large, about $100 billion on average, so we re-ran the split inside five market-cap buckets. In every bucket the crowded fifth fell 3 to 13 points more over the two weeks than the average stock of that size. It fell 4 to 16 points more than the conviction fifth. Measured against their own sectors, the crowded names still fell 6 points more than their sector peers over the two weeks, and the conviction names beat theirs by 2. Size does not explain it, and sector explains only part of it.

When Crowding Gets Punished

What made this year different is the shape of the crowd. Crowded names usually spread across the market and trade like it, as they did through every shock since 2016. This year 40% or more were in technology, against a ten-year norm of 27%. A crowd that narrow trades like one position, and when funds cut it, it fell as one.

Crowded names fall on their own when hedge funds cut a trade they share. In eleven years of data that has happened three times, all in the past twelve months: November 2025, March 2026 and October to November this year. Each time the market was down 3 to 8% and the crowded names were down 9 to 21% over three to four weeks, and each followed two months in which the crowd had run six to eleven points ahead of the market. Both earlier times, the crowded names led the recovery.

All of it sits in two fields of S3’s positioning data: how many hedge funds hold a stock, and how much.

The information herein (some of which has been obtained from third party sources without verification) is believed by S3 Partners, LLC (“S3 Partners”) to be reliable and accurate. Neither S3 Partners nor any of its affiliates makes any representation as to the accuracy or completeness of the information herein or accepts liability arising from its use. Prior to making any decisions based on the information herein, you should determine, without reliance upon S3 Partners, the economic risks, and merits, as well as the legal, tax, accounting, and investment consequences, of such decisions.