---
schema_version: "secwatch.filing_event.v1"
accession: "0000776867-24-000018"
form_type: "8-K"
ticker: "WTM"
cik: "0000776867"
company_name: "WHITE MOUNTAINS INSURANCE GROUP LTD"
filed_at: "2024-11-06T23:59:59+00:00"
generated_at: "2026-05-30T04:57:18.816142+00:00"
event_type: "earnings"
sentiment: "positive"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# White Mountains Q3 ABVPS up 6% to $1,883; Ark combined ratio improves to 79%

## Summary
- Adjusted book value per share of $1,883, up 6% in Q3 and 11% YTD including dividends.
- Ark reported combined ratio of 79% (vs 81% prior year) and GWP of $374M (+49% YoY).
- BAM deconsolidation effective July 1; surplus notes fair valued at $411M, causing $99M pre-tax unrealized loss.
- Bamboo managed premiums doubled to $148M; MGA adjusted EBITDA hit record $19M.
- MediaAlpha share price up 38% to $18.11; contributed $88M unrealized gain in Q3.

## SEC filing metadata
- accession: 0000776867-24-000018
- form_type: 8-K
- ticker: WTM
- cik: 0000776867
- company_name: WHITE MOUNTAINS INSURANCE GROUP LTD
- filed_at: 2024-11-06T23:59:59+00:00
- event_type: earnings
- sentiment: positive
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 2.02, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/776867/000077686724000018/0000776867-24-000018-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/776867/000077686724000018/wtm-20241105.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000776867-24-000018
- JSON: https://secwatch.observer/filing/0000776867-24-000018.json
- Plain text: https://secwatch.observer/filing/0000776867-24-000018.txt

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