A $1.6B bet against net selling and rising short interest.

• Berkshire Stake Disclosure: UnitedHealth (UNH) surged +11.8% August 15th after Berkshire Hathaway disclosed a new $1.6B stake (5M+ shares) in its Q2 2025 13F filing. This is Berkshire’s first UNH investment since exiting in 2010. The announcement comes after a steep YTD decline in price tied to regulatory investigations, a large-scale cyberattack, and rising medical costs.

• Long Interest Trend: Institutional ownership has moved lower YTD, with net selling across active and passive fund holders despite Berkshire’s Q2 entry. Q1 was the last quarter of net buying. In Q2, active holdings fell 2.5% and hedge fund holdings fell 5.7%—suggesting Buffett was buying into a market where most active managers were selling. S3 Long Interest shows that Q3 to date, active exposure is down 2% while passive and hedge fund long interest are both down nearly 3%. The passive flow in part reflects the impact from Russell index removal on June 30.

• Short Interest Trend: At 17.95M shares (2% of float) and $4.9B notional as of Aug. 14, short positioning sits near a three-month high in shares but well below the YTD peak $6.9B notional in April. Shorts were up roughly $2.4B YTD heading into Aug. 15, but Buffett’s stake introduces the risk that if other large buyers follow, recent gains could quickly be given back. Positioning has increased by +4.9M shares QTD, including +1.45M in the week before the Buffett disclosure, underscoring some crowding risk if the trade reverses.

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