---
schema_version: "secwatch.filing_event.v1"
accession: "0000776867-25-000002"
form_type: "8-K"
ticker: "WTM"
cik: "0000776867"
company_name: "WHITE MOUNTAINS INSURANCE GROUP LTD"
filed_at: "2025-02-07T23:59:59+00:00"
generated_at: "2026-05-27T01:14:41.825621+00:00"
event_type: "earnings"
sentiment: "negative"
materiality_score: 0.8
calibrated_materiality_score: 0.8
confidence: "high"
source: SEC EDGAR
---

# White Mountains Q4 ABVPS down 3% on $122M MediaAlpha loss; full-year ABVPS up 8%

## Summary
- Adjusted book value per share $1,834 at Dec 31, 2024, down 3% QoQ; full-year gain 8% including dividends.
- Comprehensive loss attributable to common shareholders $131M in Q4 2024 vs $288M income in Q4 2023.
- Ark combined ratio 77% in Q4; gross written premiums $264M (+14% YoY); Kudu portfolio exceeds $1B.
- Bamboo managed premiums doubled to $484M; MGA adjusted EBITDA $53M, up seven-fold YoY.
- MediaAlpha share price fell 38% to $11.29; $122M mark-to-market loss. Undeployed capital ~$700M.

## SEC filing metadata
- accession: 0000776867-25-000002
- form_type: 8-K
- ticker: WTM
- cik: 0000776867
- company_name: WHITE MOUNTAINS INSURANCE GROUP LTD
- filed_at: 2025-02-07T23:59:59+00:00
- event_type: earnings
- sentiment: negative
- materiality_score: 0.8
- calibrated_materiality_score: 0.8
- confidence: high
- sec_items: 2.02, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/776867/000077686725000002/0000776867-25-000002-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/776867/000077686725000002/wtm-20250207.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000776867-25-000002
- JSON: https://secwatch.observer/filing/0000776867-25-000002.json
- Plain text: https://secwatch.observer/filing/0000776867-25-000002.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.