White Mountains Insurance Group shares moved lower on May 6, 2026 as investors digested the company’s newly filed Q1 2026 quarterly report (Form 10-Q), which showed a sharp year-over-year earnings reversal. The company reported revenue of $517.8 million for the quarter and a net loss attributable to common shareholders of $27.2 million, translating to diluted EPS of $(12.59), compared with net income of $33.9 million and diluted EPS of $13.19 in Q1 2025. (tradingview.com)

The quarter’s headline drag was investment performance rather than core insurance operations. White Mountains recorded $65.2 million of net realized and unrealized losses tied to its MediaAlpha position, and total net realized and unrealized investment results swung to a loss of $54.4 million versus gains of about $50.0 million in the prior-year quarter. (stocktitan.net)

In the insurance business, Ark/WM Outrigger posted net earned premiums of $373.8 million and benefited from $18.3 million of favorable prior-year reserve development, helping cushion the blow from investment marks. Capital return remained active, with the company repurchasing 12,622 shares for $26 million during Q1 at an average price around $2,057, cited as roughly 95% of book value per share at March 31, 2026. (stocktitan.net)

White Mountains is a book-value-focused insurer/investment holding company, so quarter-to-quarter stock moves often track reported marks on equity stakes and realized/unrealized investment gains rather than premium growth alone. With the filing highlighting MediaAlpha-driven volatility, traders appear to be repricing near-term earnings quality and the path of book value growth into the next quarter. (stocktitan.net)