Arch Capital Group Ltd.

Arch Capital Group Ltd. is a Bermuda-based specialty insurer that underwrites property, casualty, and mortgage risk worldwide through three businesses — insurance, reinsurance, and mortgage insurance — writing $16.5 billion of net premiums and earning $4.4 billion of net income available to common shareholders in fiscal 2025. It is a member of the S&P 500 and ended the year with roughly $26.9 billion of total capital.

This is a story about a disciplined underwriter at the top of its game, walking into the part of the cycle it was built for. Over nearly 25 years Arch has compounded book value per share at a double-digit rate by leaning into hard markets and retreating from soft ones, and 2025 was close to a model year: an 82.8% combined ratio, a 20.1% return on average common equity, and book value per share up to $65.11 from $53.11. The complication is what comes next. Property-catastrophe reinsurance rates are down double digits from their 2023 peak, alternative capital is flooding back, and competition is seeping into casualty lines.

The file turns on a single question: whether Arch's celebrated cycle-management discipline can keep returns in the mid-to-high teens — and book value compounding — as the soft market deepens, or whether falling prices, casualty reserve risk, and a deliberately shrinking property book erode the franchise economics that justify a premium to book value. Everything else here is in service of that question.