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About Aon

Aon plc is a global professional services firm built around risk, retirement, and health advisory, operating as one of the two largest commercial insurance and reinsurance brokers in the world alongside Marsh McLennan. The business is organized into two reportable segments: Risk Capital, which houses commercial risk brokerage and treaty and facultative reinsurance placement, and Human Capital, which covers health benefits brokerage, retirement and pension consulting, and talent and rewards advisory. Commercial risk brokerage generates the largest share of revenue, while reinsurance is a smaller but structurally higher-margin line. The end customers span multinational corporations, middle-market firms, insurers themselves, and public-sector bodies, with fees and commissions rather than underwriting risk driving the economics.

Serious holders track the durability of organic revenue growth, since brokerage is a fee business exposed to underlying insurance pricing cycles, client retention, and new-business production. The 2024 acquisition of NFP brought material goodwill and debt onto the balance sheet, so leverage trajectory and integration execution are watched closely, as are free cash flow conversion and the pace of share repurchases relative to dividends. Regulatory exposure spans insurance intermediary licensing, fiduciary rules on retirement advice, data protection regimes, and antitrust scrutiny of broker consolidation. Governance points of interest include Aon's Irish domicile after its 2020 redomiciliation, the aborted Willis Towers Watson merger, and the concentration of institutional ownership typical of large-cap financials.

Aon traces its lineage to Combined Insurance Company of America, founded by W. Clement Stone in 1919, which merged with Ryan Insurance Group in 1982 under Patrick Ryan to form the group later renamed Aon in 1987. Through the 1990s and 2000s the firm assembled its brokerage footprint via acquisitions including Alexander & Alexander and Bain Hogg, and it exited underwriting to focus on advisory. It redomiciled from Chicago to London in 2012 and again to Ireland in 2020. A proposed 2020-2021 combination with Willis Towers Watson was abandoned after U.S. antitrust opposition. The 2024 acquisition of NFP added a middle-market brokerage platform operated as an independent unit.

The company earns commissions from insurance and reinsurance carriers on placed policies and fees from corporate and institutional clients for advisory work in health, retirement, actuarial, investment, and human capital services. Contracts range from transactional annual placements to multi-year outsourced administration and consulting engagements, with recurring renewals underpinning the revenue base. Competitive position rests on scale in reinsurance treaty placement, proprietary data and analytics assets used in risk quantification, and long-standing relationships with global corporate risk managers and pension trustees. Principal rivals are Marsh McLennan, Willis Towers Watson, Arthur J. Gallagher, and, in the middle market, Brown & Brown. The United States is the largest single geography, but a substantial share of revenue originates in EMEA and Asia Pacific.

Company profile by LineVest editorial. Journalism, not investment advice. Commission a full SEC-based report on Aon →