---
schema_version: "secwatch.filing_event.v1"
accession: "0000776867-25-000005"
form_type: "8-K"
ticker: "WTM"
cik: "0000776867"
company_name: "WHITE MOUNTAINS INSURANCE GROUP LTD"
filed_at: "2025-05-07T23:59:59+00:00"
generated_at: "2026-05-22T09:51:04.802171+00:00"
event_type: "earnings"
sentiment: "neutral"
materiality_score: 0.6
calibrated_materiality_score: 0.6
confidence: "high"
source: SEC EDGAR
---

# White Mountains Q1 book value per share $1,752 (+0.4%); Ark combined ratio 94%, gross premiums up 27%

## Summary
- Comprehensive income $35M vs $236M prior year; MediaAlpha unrealized loss $37M vs gain $211M.
- Ark gross written premiums $1,108M (+27% YoY); combined ratio 94% includes $75M California wildfire losses.
- Bamboo MGA adjusted EBITDA $20M (3x YoY); managed premiums $147M (+63%); $160M wildfire losses within reinsurance.
- Kudu adjusted EBITDA $16M (+14% YoY); trailing 12-month ROE 13%; completed Homestead farmland investment.
- Total consolidated portfolio return ex-MediaAlpha 2.3% vs 1.2% prior year; undeployed capital ~$550M after April deployments.

## SEC filing metadata
- accession: 0000776867-25-000005
- form_type: 8-K
- ticker: WTM
- cik: 0000776867
- company_name: WHITE MOUNTAINS INSURANCE GROUP LTD
- filed_at: 2025-05-07T23:59:59+00:00
- event_type: earnings
- sentiment: neutral
- materiality_score: 0.6
- calibrated_materiality_score: 0.6
- confidence: high
- sec_items: 2.02, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/776867/000077686725000005/0000776867-25-000005-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/776867/000077686725000005/wtm-20250506.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000776867-25-000005
- JSON: https://secwatch.observer/filing/0000776867-25-000005.json
- Plain text: https://secwatch.observer/filing/0000776867-25-000005.txt

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