White Mountains Insurance Group, Ltd. (WTM) Institutional Ownership

Based on Q1 2026 13F filings, institutional ownership of White Mountains Insurance Group, Ltd. stands at 91.8%, held across 357 reporting institutions.

DIMENSIONAL FUND ADVISORS LP is the largest reported institutional holder of WTM, with approximately 156,618 shares worth $0.34B as of Q1 2026.

No marquee "smart money" managers (Berkshire, Burry, ARK, Tiger Global, Pershing Square, Baupost, etc.) currently appear among the top 25 institutional holders of WTM.

Our composite Smart Money Score for WTM is 48 out of 100 (Neutral). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.

48 institutions opened new positions in WTM during Q1 2026, while 40 fully exited. 241 added to existing positions and 67 trimmed.

WTM institutional ownership rose by 3.52 percentage points quarter-over-quarter, with a net change of +8 holders.

The top 10 institutions account for 53.1% of all reported 13F value in WTM, and the top 25 account for 78.1%.

All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.