White Mountains Insurance Group posted a sharp rebound in earnings in 2025, supported by a landmark MGA divestment, disciplined underwriting, and strong investment performance.
The company reported comprehensive income attributable to common shareholders of $837 million in the fourth quarter and $1.109 billion for the full year, compared with a loss of $131 million in Q4 2024 and income of $230 million for the prior year.
While results across the broader health insurance sector were generally solid but incremental in 2025 reflecting higher utilization and medical inflation offset by disciplined pricing White Mountains’ performance stood out for its scale and steep improvement. The rebound was driven by sizable capital gains, robust underwriting results, and favorable investment returns.
Book value growth and capital deployment
Book value per share rose to $2,188 as of December 31, 2025, representing an 18% increase in the fourth quarter and 25% growth for the full year, including dividends. The largest contributor was the sale of California-focused MGA Bamboo, which added approximately $320 per share to book value and generated a net gain of $816 million for the year after compensation costs.
Excluding MediaAlpha, White Mountains’ investment portfolio returned 2.0% in Q4 and 8.9% for the full year, while the consolidated portfolio delivered returns of 2.3% and 9.1%, respectively.
CEO Liam Caffrey described 2025 as “an excellent year,” citing the Bamboo transaction, “solid results” from operating companies, and “good investment returns”.
During the quarter, the group repurchased $193 million of stock, bringing full-year repurchases to $203 million. White Mountains ended 2025 with approximately $1 billion of undeployed capital, positioning it to pursue further investment and acquisition opportunities.
Underwriting performance
The Ark/WM Outrigger segment recorded combined ratios of 77% in Q4 and 81% for the full year, with gross written premium increasing to $2.557 billion from $2.207 billion in 2024. Ark delivered a full-year combined ratio of 83% and 16% growth in gross written premiums, despite catastrophe losses from Hurricane Melissa and the January 2025 California wildfires.
WM Outrigger Re improved its combined ratio to 57% for 2025, compared with 60% in the prior year, reflecting improved underwriting profitability.
Diversification and strategic activity
HG Global returned to profitability, swinging from a $66 million pre-tax loss in 2024 to $45 million of pre-tax income in 2025, highlighting the group’s exposure to municipal finance alongside traditional insurance lines.
Kudu Investment Management generated $183 million in total revenues, $140 million in pre-tax income, and a 13% return on equity, reflecting growing contributions from asset-management and investment activities.
Distinguished, acquired in September 2025, contributed $145 million of managed premiums and $43 million in commission and fee revenue in the fourth quarter, alongside ScaleCo adjusted EBITDA of $9 million, although the business recorded a pre-tax loss as integration and growth investments continued.
Bamboo, sold to CVC Capital Partners for $848 million in net cash proceeds, produced $766 million of managed premiums and $106 million of MGA adjusted EBITDA prior to the sale. White Mountains retained a 15% fully diluted equity interest valued at approximately $250 million.
Meanwhile, MediaAlpha’s share price increase lifted the carrying value of White Mountains’ 27% stake to $231 million, with each $1 movement in the stock now shifting book value per share by around $7.
Overall, White Mountains’ 2025 results reflected a year marked by active capital allocation, disciplined underwriting, and strong investment execution, setting the group apart from more incremental earnings trends seen elsewhere in the insurance sector.
