---
schema_version: "secwatch.filing_event.v1"
accession: "0000776867-23-000016"
form_type: "8-K"
ticker: "WTM"
cik: "0000776867"
company_name: "WHITE MOUNTAINS INSURANCE GROUP LTD"
filed_at: "2023-11-06T23:59:59+00:00"
generated_at: "2026-06-08T21:39:34.658843+00:00"
event_type: "earnings"
sentiment: "neutral"
materiality_score: 0.8
calibrated_materiality_score: 0.8
confidence: "high"
source: SEC EDGAR
---

# White Mountains Q3 ABVPS up 1% to $1,588; acquires Bamboo, launches WM Partners

## Summary
- Book value per share $1,542, adjusted $1,588, both up 1% in Q3 and 6% YTD including dividends.
- BAM gross written premiums & MSC $36M in Q3 vs $46M a year ago; Ark combined ratio 81% (87% year ago).
- WM Outrigger Re combined ratio 44%, pre-tax income $37M; Kudu annualized adjusted EBITDA grew to $47M.
- MediaAlpha share price decline reduced ABVPS by 1%; carrying value $189M vs $236M at June 30.
- Announced acquisition of Bamboo and launch of WM Partners; undeployed capital roughly $400M.

## SEC filing metadata
- accession: 0000776867-23-000016
- form_type: 8-K
- ticker: WTM
- cik: 0000776867
- company_name: WHITE MOUNTAINS INSURANCE GROUP LTD
- filed_at: 2023-11-06T23:59:59+00:00
- event_type: earnings
- sentiment: neutral
- 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/776867/000077686723000016/0000776867-23-000016-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/776867/000077686723000016/wtm-20231106.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000776867-23-000016
- JSON: https://secwatch.observer/filing/0000776867-23-000016.json
- Plain text: https://secwatch.observer/filing/0000776867-23-000016.txt

## Key facts
- Earnings Releases
  WHITE MOUNTAINS INSURANCE GROUP LTD reported financial results for three months ended September 30, 2023.
  - Period: three months ended September 30, 2023
  - Result: reported results
  source text: On November 6, 2023, White Mountains Insurance Group, Ltd. issued a press release announcing its results for the three and nine months ended September 30, 2023.
  evidence_url: https://www.sec.gov/Archives/edgar/data/776867/000077686723000016/0000776867-23-000016-index.htm
- Earnings Releases
  WHITE MOUNTAINS INSURANCE GROUP LTD reported financial results for nine months ended September 30, 2023.
  - Period: nine months ended September 30, 2023
  - Result: reported results
  source text: On November 6, 2023, White Mountains Insurance Group, Ltd. issued a press release announcing its results for the three and nine months ended September 30, 2023.
  evidence_url: https://www.sec.gov/Archives/edgar/data/776867/000077686723000016/0000776867-23-000016-index.htm

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