Marsh & McLennan Companies, Inc.

Marsh & McLennan Companies, Inc. is the world's largest insurance brokerage and a premier professional services firm, generating $27.0 billion in revenue in fiscal 2025 through four businesses — Marsh Risk (insurance broking), Guy Carpenter (reinsurance), Mercer (health, wealth, and career consulting), and Oliver Wyman (management consulting) — that operate across 130 countries with roughly 95,000 employees.

This is a story about a capital-light compounding machine that has delivered 18 consecutive years of adjusted operating margin expansion while consolidating a fragmented industry through disciplined M&A. The company generates substantial free cash flow — $5.0 billion in FY2025 — and returns nearly all of it to shareholders through dividends and buybacks, making it one of the more predictable compounding stories in the S&P 500. In October 2025, management announced a historic rebrand: Marsh McLennan would become simply "Marsh," and the four legacy businesses would unify under a single brand identity beginning in 2027.

The file turns on a deceptively simple question: whether the margin-expansion streak can continue in an environment of moderating insurance pricing, rising wage costs, and genuine uncertainty about how AI will reshape the brokerage industry. The company's bet — embodied in the Thrive restructuring program, the Business and Client Services unit, and the rebrand — is that scale, data, and technology create a widening moat, not a narrowing one.