White Mountains reports 3% book value growth

Company also sells majority stake in Bamboo
White Mountains reports 3% book value growth
INSURANCE NEWS
By Josh Recamara
Nov 07, 2025

White Mountains Insurance Group reported book value per share of $1,851 as of Sept. 30, marking a 3% increase for Q3 and 6% for the first nine months of the year, including dividends. 

The company's financial position is expected to further strengthen following the sale of a controlling stake in Bamboo, its California-based managing general agent (MGA). 

Last month, White Mountains announced an agreement to sell about 77% of its equity interest in Bamboo to CVC Capital Partners, retaining a minority position. The transaction is expected to add roughly $325 per share to the group's book value once it closes in Q4, raising its pro forma book value per share to $2,176 and increasing undeployed capital from about $300 million to $1.1 billion.

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Chief executive officer Manning Rountree said Q3 performance was supported by strong operating results and investment gains across subsidiaries.

Ark achieved a combined ratio of 76% and wrote $366 million in gross premiums during the quarter, while HG Global grew book value by 3% with $16 million in gross written premiums. Kudu recorded a 9% return on equity, driven by fair value growth in its participation contracts and higher EBITDA. Bamboo also posted a record quarter, with managed premiums and adjusted EBITDA continuing to rise.

Rountree said the investment portfolio, excluding MediaAlpha, gained 2% during the quarter with contributions from both fixed income and equities. The company also completed previously announced capital deployments at BroadStreet Partners and Distinguished Programs.

Within the Ark/WM Outrigger segment, the combined ratio improved to 73% from 77% a year earlier, benefiting from minimal catastrophe losses and improved underwriting in property and specialty lines. Ark's year-to-date combined ratio was 84%, reflecting wildfire-related losses in California earlier in the year but fewer catastrophe impacts overall.

Ark reported pretax income of $97 million for the quarter, compared with $119 million a year earlier, with CEO Ian Beaton noting that year-to-date gross written premiums rose 18% to $2.3 billion due to new underwriting teams and classes of business.

HG Global delivered steady performance with 24% year-over-year growth in par value assumed, while Kudu's revenue rose to $54 million for the quarter on strong investment income and portfolio diversification.

Bamboo, which recently expanded into Texas, reported commission and fee revenue of $64 million for the quarter, up from $43 million in the prior year, with managed premiums of $221 million. CEO John Chu said the firm's strong results and geographic expansion have positioned it for continued profitable growth.

White Mountains’s total investment portfolio returned 2.1% for the quarter, or 2% excluding MediaAlpha, reflecting steady performance despite equity market volatility.

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