White Mountains Insurance Group Reports 25% BVPS Growth in 2025.

White Mountains Insurance Group reported a book value per share of $2,188 as of December 31, 2025, an 18% increase for Q4 and 25% for the year. The growth was mainly driven by the net gain from the sale of Bamboo and solid results from operating companies, including Ark's 83% combined ratio and $2.6 billion of gross written premiums, up 16%.