Arthur J. Gallagher & Co.

Arthur J. Gallagher & Co. is an American insurance brokerage, risk management, and consulting firm that places commercial property/casualty, reinsurance, and employee benefits coverage for clients in approximately 130 countries while operating one of the world's largest third-party claims administration businesses under the Gallagher Bassett brand, generating $13.9 billion in total revenue in fiscal 2025. The company employs approximately 72,000 people, has completed over 750 acquisitions since 2000, and in August 2025 closed the $13.8 billion purchase of AssuredPartners — the largest acquisition in its history and a transaction that roughly doubled its U.S. middle-market retail brokerage footprint.

This is a story about two compounding engines running in parallel. The first is an organic growth machine built on high client retention, steady new business wins, and a diversified book spanning property/casualty, employee benefits, reinsurance, and claims administration — businesses that have grown through both hard and soft insurance markets. The second is a serial acquisition program that has deployed billions into tuck-in deals at attractive arbitrage spreads, funded by prodigious free cash flow and periodic equity issuance. The file turns on a single question: whether Gallagher can sustain its historical organic growth trajectory in a softening property market while simultaneously integrating the largest acquisition in its history — and whether the market's current discount to the sum of those parts is warranted.