Item 1. Business.

References in this report to "we", "us" and "our" are to Marsh & McLennan Companies, Inc. and its consolidated subsidiaries (the "Company" or "Marsh McLennan"), unless the context otherwise requires.

GENERAL

Marsh McLennan is the world's leading professional services firm in the areas of risk, strategy and people. We help clients build the confidence to thrive through the power of perspective of our four market-leading businesses. With annual revenue of $23 billion, we have more than 85,000 colleagues advising clients in over 130 countries.

Marsh provides data-driven risk advisory services and insurance solutions to commercial and consumer clients. Guy Carpenter develops advanced risk, reinsurance and capital strategies that help clients grow profitably and pursue emerging opportunities. Mercer delivers advice and technology-driven solutions that help organizations redefine the world of work, reshape retirement and investment outcomes, and unlock health and well-being for a changing workforce. Oliver Wyman Group serves as a critical strategic, economic and brand advisor to private sector and governmental clients. Our four businesses also collaborate together to deliver new solutions to help clients manage complex and interconnected risks.

The Company conducts business through two segments:

• Risk and Insurance Services** includes risk management activities (risk advice, risk transfer and risk control and mitigation solutions) as well as insurance and reinsurance broking and services. The Company conducts business in this segment through Marsh and Guy Carpenter.

• Consulting** includes health, wealth and career advice, solutions and products, and specialized management, strategic, economic and brand consulting services. The Company conducts business in this segment through Mercer and Oliver Wyman Group.

We describe our current segments in further detail below. We provide financial information about our segments in our consolidated financial statements included under Part II, Item 8 of this report.

OUR BUSINESSES

RISK AND INSURANCE SERVICES

The Risk and Insurance Services segment generated approximately 62% of the Company's total revenue in 2023 and employs approximately 49,300 colleagues worldwide. The Company conducts business in this segment through Marsh and Guy Carpenter.

MARSH

Marsh is the world's leading insurance broker and risk advisor, serving companies, institutions and individuals. From its founding in 1871 to the present day, Marsh has demonstrated a commitment to thought leadership, innovation and insurance expertise to meet its clients’ needs. Marsh’s pioneering contributions include introducing the practice of client representation through brokerage, the discipline of risk management, the globalization of risk management services and the development of service platforms that identify, quantify, mitigate and transfer risk.

Currently, approximately 45,800 Marsh colleagues provide risk management, insurance broking, insurance program management, risk consulting, analytical modeling and alternative risk financing services to a wide range of businesses, government entities, professional service organizations and individuals in over 130 countries. Marsh generated approximately 51% of the Company's total revenue in 2023.

Insurance Broking and Risk Advisory

In its core insurance broking and risk advisory business, Marsh employs a team approach to identify, quantify and address clients' risk management and insurance needs. Marsh’s product and service offerings include risk analysis, insurance program design and placement, insurance program support and administration, claims support and advocacy, alternative risk strategies and a wide array of risk analysis and risk management consulting services. Clients benefit from Marsh’s advanced analytics, deep technical expertise, specialty and industry knowledge, collaborative global culture and the ability to develop innovative solutions and products. The firm’s resources also include nearly three dozen specialty and industry practices, including cyber, construction, renewable energy, healthcare, and financial and professional service practices, along with ESG products such as

a D&O insurance initiative recognizing U.S. based clients with superior ESG frameworks, and an established employee health & benefits business.

Marsh provides services to clients of all sizes, including large multinational companies ("Risk Management"), high growth middle-market businesses ("Corporate"), small commercial enterprises and high net-worth private clients, and affinity group members ("Commercial & Consumer"). Marsh's segments are designed to build stronger value propositions and operating models to optimize solutions and services for clients depending on their needs.

Risk Management. Marsh has an extensive global footprint and market-leading advisory and placement services that benefit large domestic and international companies and institutions facing complex risk exposures. These clients are also supported by Marsh’s robust analytics and a growing digital experience.

In addition, Marsh’s largest global clients are serviced by Marsh Multinational, a dedicated team of colleagues from around the world focused on delivering service excellence and insurance solutions to clients wherever they are located. Marsh is digitizing the client experience through tools such as LINQ, Marsh’s account and service application; Blue[i], a suite of analytics tools for clients; and Bluestream, a digital brokerage platform that enables clients to provide insurance to their customers or suppliers in a B2B2C distribution model. Marsh provides global expertise and an intimate knowledge of local markets, helping clients navigate local regulatory environments to address the worldwide risk issues that confront them.

• Marsh Specialty** is an integrated and globally coordinated team of experts who provides clients in highly specialized industry and product areas with data driven insights, service, advice and access to global insurance markets. These specialists support clients who require advice and support across aviation & space, credit specialties, construction, energy & power, financial & professional services (FINPRO), marine & cargo, and private equity, mergers & acquisitions (PEMA).

Corporate. Middle market clients are served by Marsh’s brokerage operations globally; this segment is also serviced by Marsh & McLennan Agency (MMA) in the United States (U.S.).

• Marsh McLennan Agency (MMA)** provides business insurance, employee health and benefits, retirement and wealth management, and private client insurance solutions to individuals and mid-market organizations. MMA advises on insurance program structure and market dynamics, along with industry expertise and transactional capability. Since its first acquisition in 2009, MMA has acquired more than 100 agencies.

Commercial & Consumer. Clients in this market segment typically face less complex risks and are served by Marsh’s innovative product and placement offerings and growing capabilities in digitally enabled distribution and administration.

• Victor Insurance Managers (Victor**) is one of the largest underwriting managers of professional liability, catastrophe, and other specialty insurance programs worldwide. In the U.S., Victor Insurance Managers (US) and ICAT Managers underwrites, solicits, sells and services coverages through a national third-party distribution network of licensed brokers and agents. Through its Victor Small Business platform, Victor deploys cloud-based technology to enable independent insurance agents, on behalf of their small business clients, to obtain online quotes from multiple insurance providers and bind property and casualty and workers compensation insurance policies in real time. Victor also manages Torrent Technologies, the nation’s largest service provider to the National Flood Insurance Program (NFIP), serving the NFIP both directly and through the NFIP’s Write Your Own (WYO) program. Victor Insurance Managers (Canada), a leading managing general agent in Canada, delivers professional liability and construction insurance and other P&C programs and administers group and retiree benefits programs and claims handling operations for individuals, organizations and businesses. Victor also has a business in the UK, the Netherlands, Italy, Germany and Australia.

• Marsh Affinity** focuses on insurance programs sold to insureds or vendors through a corporate sponsor using an affinity distribution model.

• High Net Worth (HNW).** Individual high net worth clients and family offices are serviced by MMA in the U.S. and other Marsh personal lines businesses globally. These businesses provide a single-source solution for high net worth clients and are dedicated to sourcing protections across a broad spectrum of risk. Using a consultative approach, Marsh's HNW practices analyze exposures and customize programs to cover individual clients with complex asset portfolios.

Additional Services and Adjacent Businesses

In addition to insurance broking, Marsh provides certain other specialist advisory or placement services:

Marsh Advisory is a global practice comprising specialists who use data and analytics, including through Marsh’s Blue[i] digital analytics platform. Marsh Advisory’s three main service areas (Consulting, Claims, and Analytics) advise clients on existing and emerging risk exposures, protecting critical business activities and developing strategies to optimize total cost of risk.

Marsh Captive Solutions*,* a prominent part of the Marsh Specialty and Global Placement practice, helps organizations of all sizes retain risks through comprehensive and innovative captive solutions. This team is comprised of captive consultants, actuaries and captive management professionals which offer complete, end-to-end captive management services.

Bowring Marsh is an international placement broker. This unit’s core strategy is to modernize risk transfer advice and solutions for clients. This is executed through a combination of data solutions, capacity creation vehicles, segmentation, placement platforms (on-shoring solutions within the network), and improved operational efficiency – all designed to yield a better client outcome and experience. The products Bowring Marsh places include property, casualty, terrorism, product recall, and special risks.

Mercer Marsh Benefits provides health benefits brokerage and consulting services to clients of all sizes in numerous countries across the globe, outside of the U.S. As described below, Mercer and Marsh go to market together to provide strategic advice and services to help clients minimize risk, optimize benefits structure, drive efficiencies and maximize employee engagement.

Services for Insurers

Marsh's Insurer Consulting Group (ICG) provides services to insurance carriers. Through Marsh's patented electronic platform, MarketConnect, and sophisticated data analysis, ICG provides insurers with individualized preference setting and risk identification capabilities, as well as detailed performance data and metrics. Insurer consulting teams review performance metrics and preferences with insurers and provide customized consulting services to insurers designed to improve business planning and strategy implementation. ICG services are designed to improve the product offerings available to clients, assist insurers in identifying new opportunities and enhance insurers’ operational efficiency. The scope and nature of the services vary by insurer and by geography.

GUY CARPENTER

Guy Carpenter, the Company’s reinsurance intermediary and advisor, generated approximately 11% of the Company's total revenue in 2023. Currently, approximately 3,500 Guy Carpenter colleagues provide clients with a combination of specialized reinsurance broking expertise, strategic advisory services and analytics solutions. Guy Carpenter creates and executes reinsurance and risk management solutions for clients worldwide through risk assessment analytics, actuarial services, highly-specialized product knowledge and trading relationships with reinsurance markets. Client services also include contract and claims management, reinsurance accounting and fiduciary services.

Acting as a broker or intermediary on all classes of reinsurance, Guy Carpenter places two main types of property casualty and life / health reinsurance: treaty reinsurance, which involves the transfer of a portfolio of risks; and facultative reinsurance, which involves the transfer of part or all of the coverage provided by a single insurance policy.

Guy Carpenter provides reinsurance services in a broad range of centers of excellence, segments and specialties including: Automobile / Motor, Aviation, Captives, Crop/Agriculture, Cyber, Engineering / Construction, Financial Lines, InsurTech, Life / Accident / Health, Marine and Energy, Medical Professional, Personal Lines, Mortgage, Political Risk & Trade Credit, Primary & Excess Casualty, Managing General Agents and Program Manager Solutions, Property, Public Sector, Regional / Mutual, Retrocessional Reinsurance, Surety, Terror, and Workers Compensation / Employer Liability.

Guy Carpenter also offers clients alternatives to traditional reinsurance, including industry loss warranties and, through its licensed affiliates, capital markets alternatives such as transferring catastrophe risk through the issuance of insurance-linked securities. GC Securities, the Guy Carpenter division of MMC Securities LLC and MMC Securities (Europe) Limited, offer corporate finance solutions, including mergers & acquisitions advice and private debt and equity capital raising, and capital markets-based risk transfer solutions that complement Guy Carpenter's strong industry relationships, analytical capabilities and reinsurance expertise.

Guy Carpenter also provides its clients with reinsurance-related services, including actuarial, enterprise risk management, financial and regulatory consulting, portfolio analysis and advice on the efficient use of capital. Guy Carpenter's Global Strategic Advisory ("GSA") unit helps clients better understand and quantify the uncertainties inherent in their businesses. Working in close partnership with Guy Carpenter account executives, GSA specialists help support clients' critical decisions in numerous areas, including reinsurance utilization, catastrophe exposure portfolio management, new product and market development, rating agency, regulatory and account impacts, loss reserve risk, capital adequacy and return on capital.

Compensation for Services in Risk and Insurance Services

Marsh and Guy Carpenter are compensated for brokerage and consulting services through commissions and fees. Commission rates and fees vary in amount and can depend on a number of factors, including the type of insurance or reinsurance coverage provided, the particular insurer or reinsurer selected, and the capacity in which the broker acts and negotiates with clients. In addition to compensation from its clients, Marsh also receives other compensation, separate from retail fees and commissions, from insurance companies. This other compensation includes, among other things, payments for consulting and analytics services provided to insurers; compensation for administrative and other services (including fees for underwriting services and services provided to or on behalf of insurers relating to the administration and management of quota shares, panels and other facilities in which insurers participate); and contingent commissions, which are paid by insurers based on factors such as volume or profitability of Marsh's placements, primarily driven by MMA and parts of Marsh's international operations.

Marsh and Guy Carpenter receive interest income on certain funds (such as premiums and claims proceeds) held in a fiduciary capacity for others. For a more detailed discussion of revenue sources and factors affecting revenue in our Risk and Insurance Services segment, refer to Part II, Item 7 ("Management's Discussion and Analysis of Financial Condition and Results of Operations") of this report.

CONSULTING

The Company's Consulting segment generated approximately 38% of the Company's total revenue in 2023 and employs approximately 31,300 colleagues worldwide. The Company conducts business in this segment through Mercer and Oliver Wyman Group.

MERCER

Mercer is a leading provider in delivering advice, solutions and products that help organizations meet the health, wealth and career needs of a changing workforce. Mercer has approximately 24,500 colleagues based in 48 countries. Clients include a majority of the companies in the Fortune 1000 and FTSE 100, as well as medium- and small-market organizations, public sector entities and individual customers. Mercer generated approximately 24% of the Company's total revenue in 2023.

Mercer operates in the following areas:

Health. Mercer helps public and private sector employers design and manage employee health and welfare programs; administer health benefits and flexible benefits programs, including benefits outsourcing; engage employees with their health benefits through a digital experience; and comply with local benefits-related regulations. Mercer provides a range of advice and solutions to clients, which, depending on the engagement, may include: total health and wellness management strategies; global health brokerage solutions; vendor performance and audit; life and disability management; and measurement of healthcare provider performance. These services are provided through fee-based consulting as well as commission-based brokerage services in connection with the selection of insurance companies and healthcare providers.

Mercer also provides consulting and actuarial services to U.S. state governments to support the purchase of healthcare through state Medicaid programs. Mercer offers clients tools to enhance employee engagement with their health benefits through its DarwinSM platform.

Outside of the U.S., Mercer and Marsh go to market together for Health benefits brokerage and consulting under the Mercer Marsh BenefitsSM (MMB) brand, as described above.

Wealth. Through its Wealth business, Mercer assists clients worldwide in the design, governance and risk management of defined benefit, defined contribution, hybrid retirement plans and other pools of assets, and with investment of those assets.

Mercer provides actuarial consulting, investment consulting, investment management and related services to the sponsors and trustees of pension plans, master trusts, foundations, endowments, sovereign wealth funds, insurance companies and family offices. Mercer also provides investment consulting and investment management services to U.S. public sector clients, financial intermediaries and individuals. Mercer provides retirement plan outsourcing, including administration and delivery of defined benefit and defined contribution retirement benefits.

Mercer's investment consulting and investment management services (investment management services may also be referred to as "investment solutions," "delegated solutions," "fiduciary management" or "outsourced Chief Investment Officer (OCIO) services") cover a range of stages of the investment process, from investment research (through its Mercer-Insight service), asset allocation and implementation of investment strategies to ongoing portfolio management services. Mercer provides these services primarily to institutional and other sophisticated investors including retirement plans (e.g., defined benefit and defined contribution), master trusts, endowments and foundations, sovereign wealth funds, U.S. public sector clients, insurance companies and family offices, as well as wealth managers and other financial intermediaries, primarily through manager of manager strategies and funds sponsored and managed by Mercer. Mercer’s clients invest in both traditional asset classes (e.g., equities, fixed income and cash equivalents) and alternative or private market strategies (e.g., private equity, private debt, real estate, other real assets and hedge funds). As of December 31, 2023, Mercer and its global affiliates had assets under management of approximately $420 billion worldwide.

Mercer also provides services to individual retail clients, including financial planning, high net worth risk solutions and other discretionary investment services.

Career. Mercer advises organizations on the engagement, skill assessment, management and reward of employees; the design of executive remuneration programs; people and workforce strategies during business transformation; improvement of human resource (HR) effectiveness; and the implementation of digital and cloud-based Human Resource Information Systems. In addition, through proprietary survey data and decision support tools, Mercer provides clients with human capital information and analytical capabilities to improve strategic human capital decision making. Mercer’s Career products include solutions relating to rewards, mobility, engagement, workforce analytics and assessments. Mercer helps clients plan and implement HR programs and other organizational changes designed to maximize employee engagement.

Mercer also provides advice relating to people and benefits-related issues to buyers and sellers in a variety of types of M&A transactions.

OLIVER WYMAN GROUP

With more than 6,800 professionals and offices in over 30 countries, Oliver Wyman Group delivers advisory services to clients through three operating units, each of which is a leader in its field: Oliver Wyman, Lippincott and NERA Economic Consulting. Oliver Wyman Group generated approximately 14% of the Company's total revenue in 2023.

Oliver Wyman is a global leader in management consulting and combines deep industry knowledge with specialized expertise in strategy, operations, risk management and organization transformation. The firm works with clients around the world to help optimize their business, improve their operations and risk profile, and accelerate their organizational performance to seize attractive opportunities. Industry groups include:

• Automotive and Manufacturing Industries

• Communications, Media & Technology

• Energy and Natural Resources

• Financial Services (including corporate and institutional banking, public policy, and retail and business banking)

• Insurance and Asset Management

• Health and Life Sciences

• Public Sector

• Private Capital

• Retail & Consumer Goods

• Transportation Services (including aviation; aerospace and defense; rail; express, postal and third party logistics; services, including travel and leisure, environmental and facility management, and business and tech services; and CAVOK, which provides technical consulting and market forecasting services)

Oliver Wyman overlays its industry knowledge with expertise in the following functional specializations:

• Actuarial. Oliver Wyman’s Actuarial Practice uses mathematical and statistical modeling skills and qualitative assessment methodologies to assist clients in evaluating and addressing risk.

• Climate and Sustainability. Oliver Wyman assists clients in cutting through complex climate systems and solving for operational efficiencies. Oliver Wyman helps clients discover new business opportunities, create new pathways, and respond to climate risk, to make needed changes commercially compelling.

• Finance and Risk. Oliver Wyman provides leading financial institutions with custom solutions and insights covering all aspects of risk and finance functions, including credit risk, market risks, asset and liability management and liquidity risks, and non-financial risks, together with integrated risk management topics, such as aggregated risk analyses, business applications and culture and organization.

• Restructuring. Oliver Wyman offers a complete management solution and "one-stop-shop" approach to turning around companies, providing strategic, operational, and financial restructuring advice.

• Digital. Oliver Wyman partners with clients to address their digital challenges, blending the power of digital with deep industry expertise. By building strong capabilities and culture, Oliver Wyman accelerates and embeds digital transformation, working collaboratively with clients’ leaders, employees, stakeholders, and customers to jointly define, design, and achieve lasting results.

• Operations. Oliver Wyman helps organizations leverage their operations for a competitive advantage using a comprehensive set of capabilities, including performance improvement, digital operations strategy, and risk management.

• People and Organizational Performance. Oliver Wyman's People and Organizational Performance capability brings together deep functional expertise and industry knowledge to enable the whole organization to work in service of its strategic vision and to address the most pressing organizational, people, and change issues.

• Payments. Oliver Wyman draws on years of industry-shaping work in the Financial Services and Retail industries, deep digital expertise, and renowned research partners in its Celent® business, to help clients - from banks/issuers, to payments providers, to retailers - to build growth strategies, form effective partnerships, optimize costs, and manage risk.

• Pricing, Sales, and Marketing. Oliver Wyman helps organizations drive top-line and margin growth through outstanding strategy and decision making on pricing, marketing optimization, and best practices on sales effectiveness.

• Customer First. Oliver Wyman helps bring together capabilities required to identify customer and business growth, conduct detailed business design, build and launch a business, and maintain a focus on realizing growth while de-risking delivery.

• Performance Transformation. Oliver Wyman helps clients to design, realize and sustain value growth via large-scale transformations.

Lippincott is a creative consultancy specializing in brand and innovation that shapes recognized brands and experiences for clients globally. Lippincott's designers have helped create some of the world's most recognized brands.

NERA Economic Consulting provides economic analysis and advice to public and private entities to achieve practical solutions to highly complex business and legal issues arising from competition, regulation, public policy, strategy, finance and litigation. NERA professionals operate worldwide assisting clients including corporations, governments, law firms, regulatory agencies, trade associations, and international agencies. NERA's specialized practice areas include: antitrust; securities; complex commercial litigation; energy; environmental economics; network industries; intellectual property; product liability and mass torts; and transfer pricing.

Compensation for Services in Consulting

Oliver Wyman Group is compensated for advice and services primarily through fees paid by clients. Mercer is compensated for advice and services through fees paid by clients, commissions and fees based on assets or members. In the majority of cases, Mercer's Health business is compensated through commissions for the placement of insurance contracts and supplemental compensation from insurers based on such factors as volume, growth of accounts, and total retention of accounts placed by Mercer. Mercer may receive commissions in other parts of its business, such as its Private Client Services business and certain financial advice businesses. Mercer's investments business and certain of Mercer's administration services are compensated typically through fees based on assets under administration or management or fee per member. For a majority of the Mercer-managed investment funds, revenue received from Mercer's investment management clients as sub-advisor fees is reported in accordance with U.S. GAAP, on a gross basis rather than a net basis. For a more detailed discussion of revenue sources and factors affecting revenue in the Consulting segment, refer to Part II, Item 7 ("Management's Discussion and Analysis of Financial Condition and Results of Operations") of this report.

REGULATION

The Company's activities are subject to licensing requirements and extensive regulation under U.S. federal and state laws, as well as laws of other countries in which the Company operates. Across most jurisdictions, we are also subject to various data privacy and data protection laws and regulations that apply to personal information, as well as, in certain jurisdictions, cybersecurity laws and regulations and emerging laws and regulations related to artificial intelligence ("AI"). In addition, we are subject to various financial crime laws and regulations through our activities, activities of associated persons, the products and services we provide and our business and client relationships. Such laws and regulations relate to, among other areas, sanctions and export control, anti-bribery, anti-corruption, anti-money-laundering and counter-terrorist financing. In certain circumstances, we are also required to maintain operating funds primarily related to regulatory requirements outside the U.S. See Part I, Item 1A ("Risk Factors") below for a discussion of how actions by regulatory authorities or changes in legislation and regulation in the jurisdictions in which we operate may have an adverse effect on our businesses and for more information about the laws and regulations related to data privacy, data protection and cybersecurity and the associated risks to our businesses.

Risk and Insurance Services**.** While laws and regulations vary from location to location, every state of the U.S. and most foreign jurisdictions require insurance market intermediaries and related service providers (such as insurance brokers, agents and consultants, reinsurance brokers and managing general agents) to hold an individual or company license from a government agency or self-regulatory organization. Some jurisdictions issue licenses only to individual residents or locally-owned business entities; in those instances, if the Company has no licensed subsidiary, it may maintain arrangements with residents or business entities licensed to act in such jurisdiction. Such arrangements are subject to an internal review and approval process. Licensing of reinsurance intermediaries is generally less rigorous compared to that of insurance brokers, and most jurisdictions require only corporate reinsurance intermediary licenses.

In the United Kingdom, our business is regulated by the Financial Conduct Authority ("FCA"). The FCA’s responsibilities and powers include licensing of insurance and reinsurance intermediaries and related criteria such as professional competence, financial capacity and the requirement to hold professional indemnity insurance, the broking of premium finance to consumers, and competition powers that enable it to enforce prohibitions on anti-competitive behavior in relation to financial services.

Insurance authorities in the U.S. and certain other jurisdictions in which the Company's subsidiaries do business, including the FCA in the United Kingdom, also have enacted laws and regulations governing the investment of funds, such as premiums and claims proceeds, held in a fiduciary capacity for others. These laws and regulations typically provide for segregation of these fiduciary funds and limit the types of investments that may be made with them, and generally apply to both the insurance and reinsurance business.

Certain of the Company's Risk and Insurance Services activities are governed by other regulatory bodies, such as investment, securities and futures licensing authorities. In the U.S., Marsh and Guy Carpenter use the services of MMC Securities LLC, a SEC registered broker-dealer and introducing broker in the U.S. MMC Securities LLC is a member of the Financial Industry Regulatory Authority ("FINRA"), the National Futures Association and the Securities Investor Protection Corporation ("SIPC"), primarily in connection with capital markets and other investment banking-related services relating to insurance-linked and alternative risk financing transactions. Also in the U.S., Marsh uses the services of MMA Securities LLC, a SEC registered broker-dealer, investment adviser

and member of FINRA, SIPC and the Municipal Securities Rulemaking Board ("MSRB"), and MMA Asset Management LLC, a SEC registered investment adviser, primarily in connection with retirement, executive compensation and benefits consulting and advisory services to qualified and non-qualified benefits plans, companies and executives and personal wealth management. In the United Kingdom, Marsh and Guy Carpenter use the expertise of MMC Securities Limited, which is authorized and regulated by the FCA to provide advice on securities and investments, including mergers & acquisitions in the United Kingdom. In the European Union, Guy Carpenter uses MMC Securities (Ireland) Limited, which is authorized and regulated by the Central Bank of Ireland to place certain securities and investments in the European Union. MMC Securities LLC, MMC Securities Limited, MMC Securities (Ireland) Limited, MMA Securities LLC, and MMA Asset Management LLC are indirect, wholly-owned subsidiaries of Marsh & McLennan Companies, Inc.

Consulting*.* Mercer's retirement-related consulting and investment services are subject to pension law and financial regulation in many countries. Depending on the country, Mercer may rely on licensed colleagues or registered legal entities to engage in these services, or may utilize other Marsh McLennan entities or third parties. In addition, trustee services, investment services (including advice to persons, institutions and other entities on the investment of pension assets and assumption of discretionary investment management responsibilities) and retirement and employee benefit program administrative services provided by Mercer and its subsidiaries and affiliates may also be subject to investment and securities regulations in various jurisdictions, including (but not limited to) regulations imposed or enforced by the Securities and Exchange Commission (SEC) and the Department of Labor in the U.S., the FCA in the United Kingdom, the Central Bank of Ireland and the Australian Prudential Regulation Authority and the Australian Securities and Investments Commission. In the U.S., Mercer provides investment services through Mercer Investments LLC, (formerly Mercer Investment Management, Inc.), an SEC-registered investment adviser, which consolidated the activities of each of Mercer’s affiliated investment adviser entities in the U.S. (including Mercer Investment Consulting LLC and Pavilion Advisory Group) in 2019. Mercer Trust Company, a limited purpose New Hampshire chartered trust bank, may also provide services for certain clients of Mercer’s investment management business in the U.S. The benefits insurance consulting and brokerage services provided by Mercer and its subsidiaries and affiliates are subject to the same licensing requirements and regulatory oversight as the insurance market intermediaries described above regarding our Risk and Insurance Services businesses. Depending on the nature of the client and services performed, Mercer may also be subject to direct oversight by the Departments of Health and Human Services and other federal agencies in the U.S. Mercer provides annuity buy-out advice that is subject to regulations (for example, in the U.S., state insurance licensing regulations and ERISA). Mercer uses the services of MMC Securities LLC to provide certain services, including executive benefit and compensation services and securities dealing services.

FATCA**.** Regulations promulgated by the U.S. Treasury Department pursuant to the Foreign Account Tax Compliance Act and related legislation (FATCA) require the Company to take various measures relating to non-U.S. funds, transactions and accounts. The regulations impose on Mercer and MMA certain client financial account obligations relating to non-U.S. financial institution and insurance clients.

COMPETITIVE CONDITIONS

The Company faces significant competition in all of its businesses from providers of similar products and services, including competition with regard to identifying and pursuing acquisition candidates. The Company also encounters strong competition throughout its businesses from both public corporations and private firms in attracting and retaining qualified employees. As the Company has clients across various geographies, industries and sizes, the competitive landscape is complex and varies across numerous markets. In addition to the discussion below, refer to "Risks Relating to the Company Generally — Competitive Risks," in Part I, Item 1A of this report.

Risk and Insurance Services**.** The Company's combined insurance and reinsurance services businesses are global in scope. Our insurance and reinsurance businesses compete principally on the sophistication, range, quality and cost of the services and products they offer to clients. The Company encounters strong competition from other insurance and reinsurance brokerage firms that operate on a global, regional, national or local scale in every geography in which it operates, from insurance and reinsurance companies that market, distribute and service their insurance and reinsurance products without the assistance of brokers and from other businesses, including commercial and investment banks, accounting firms, consultants and online platforms, that provide risk-related services and products or alternatives to traditional insurance brokerage services. In addition, third party capital providers have entered the insurance and reinsurance risk transfer market offering products and capital

directly to the Company’s clients. Their presence in the market increases the competitive pressures that the Company faces.

Certain insureds and groups of insureds have established programs of self-insurance as a supplement or alternative to purchasing traditional third-party insurance, thereby reducing in some cases their need for third-party insurance placements. Certain insureds also obtain coverage directly from insurance providers. There are also many other providers of managing general agents, affinity programs and private client services that compete with the Company's offerings.

Consulting**.** The Company's consulting businesses face strong competition from other privately and publicly held worldwide and national companies, as well as regional and local firms. These businesses generally compete on the basis of the range, quality and cost of the services and products they provide to clients. Competitors include independent consulting, broking and outsourcing firms, as well as consulting, broking and outsourcing operations affiliated with larger accounting, information systems, technology and financial services firms. Mercer’s Health business faces additional competition from insurers and from non-traditional competitors seeking to enter or expand in the health benefits space (for example, payroll firms, large consumer businesses, and digitally oriented consultancies). Mercer's investments business faces competition from many sources, including investment consulting firms (many of which offer delegated services), investment management firms and other financial institutions. In some cases, clients have the option of handling the services provided by Mercer and Oliver Wyman Group internally, without assistance from outside advisors.

Segmentation of Activity by Type of Service and Geographic Area of Operation.

Financial information relating to the types of services provided by the Company and the geographic areas of its operations is incorporated herein by reference to Note 17, Segment Information, in the notes to the consolidated financial statements included under Part II, Item 8 of this report.

ENVIRONMENTAL, SOCIAL AND GOVERNANCE (ESG)****)

Since 2008, Marsh McLennan has had a framework for overseeing and managing the company’s approach to environmental sustainability, human capital management and corporate governance. Our ESG Report provides more information about our ESG governance, goals and achievements. It also discloses against aspects of the Task Force on Climate-related Financial Disclosures, Sustainability Accounting Standards Board and Global Reporting Initiative standards and describes the six UN Sustainable Development Goals we have prioritized that most relate to our business. Our ESG Report, Pay Equity Statement, statement on Human Rights and related information is available on our website at marshmclennan.com/about/esg.html. These reports and our website are not deemed part of this report and are not incorporated by reference.

HUMAN CAPITAL

As a professional services firm, we believe the health of our business relies on the strength of our workforce.

For detailed information regarding our human capital management, we encourage investors to visit https://www.marshmclennan.com/about/esg.html for our consolidated ESG Report. The information on this website, and in the ESG report, does not constitute, and should not be viewed as, incorporation by reference of the information contained on, or available through, the website or the report and does not form part of this Form 10-K.

Our People. As of December 31, 2023, the Company and its consolidated subsidiaries employed more than 85,000 colleagues worldwide, including approximately 49,300 in Risk and Insurance Services and 31,300 in Consulting. One-third of our global workforce is located in the U.S. & Canada, with approximately 15% in each of the United Kingdom, Europe and IMEA (India, Middle East, & Africa), with the remainder in Latin America & Caribbean, Asia, and Pacific. Women comprise more than half of our global enterprise workforce, and approximately 33% of our senior leaders are women. In the U.S., where we have the most complete data through workforce self-identification of race and ethnicity, approximately 1 in 4 U.S. colleagues and 18% of U.S. senior leaders identify as non-White.

Our Governance. The Chief People Officer is responsible for developing and executing our enterprise people strategy. This includes the attraction, recruitment, hiring, development and engagement of talent to deliver on our strategy and the design of colleague total rewards programs. The Chief People Officer is also responsible for developing and integrating our inclusion and diversity approach into our strategy, supported by the Chief Diversity & Social Impact Officer.

Talent & Inclusion. Our Company’s greatest strength is the collective talent of our people. We offer programs globally, regionally and business-specific that are aimed at helping us attract, develop and retain a diverse workforce. We provide resources to support colleagues in learning about diverse experiences, connecting with each other and positively impacting communities. We are committed to helping colleagues perform at their best by encouraging regular discussions about their goals, performance, career aspirations and development opportunities. We offer programming to support their growth and activate a leadership mindset for all colleagues.

We also aim to build a learning culture and deliver a digital-first learning strategy, supplemented by formal programs for key groups. For example, our 2023 Learning Festival offered 31 live sessions in 8 languages with over 18,000 attendees. Top sessions included business briefings with our CEOs, the future of insurance, cyber resilience and AI.

We also recognize the importance of our nearly 18,000 people managers to our talent pipeline and have given them increased support and opportunities for promoting the growth of their teams. In 2023 we offered 450 development workshops with courses covering professional skills, people management and leadership development. Our People Manager Hub is a one-stop digital source for people managers globally. Through the Hub, people managers have access to suggested learning, webinars and resources to support development and provide guidance.

Colleague Engagement. Each year we ask our colleagues to share their views on working at Marsh McLennan through a company-wide engagement survey. Developed internally by our Global Talent Development team, the survey methodology has been consistent since 2011, with updates to specific questions as necessary. In 2023, we expanded the survey with questions on technology and the company's strategy. A third-party administers our survey in order to maintain confidentiality of responses. Collective survey outcomes allow us to monitor the evolution of our culture over time and identify opportunities to build on strengths and address challenges, all with the intention of furthering our productivity through an engaged workforce.

Health and Well-being. As a company, our success depends on the health and well-being of our colleagues. We offer comprehensive health insurance, including medical coverage and other core health benefits based on the market. We also prioritize our colleagues’ mental wellness, including 24/7 access to an Employee Assistance Program for confidential counselling on personal issues for 99% of our colleagues and their eligible family members, and critical incident support in countries where a disaster has occurred. In addition, we offer competitive time-off benefits, including a paid day off each year to volunteer. We support our colleagues as they navigate changing circumstances—milestone life events, health and economic challenges, and new technologies.

Total Rewards. We offer competitive rewards to help build colleagues’ personal wealth and improve their financial well-being. Base pay is one component. Through our annual bonus program, we encourage performance that aligns with the Company’s interests by providing eligible colleagues with discretionary awards. We also offer various incentives in certain circumstances, such as sales incentives and long-term incentives to people in roles that have a significant impact on our long-term performance and success. Our offerings also include retirement benefits, savings and stock investment plans in certain jurisdictions.

EXECUTIVE OFFICERS OF THE COMPANY

The executive officers and executive officer appointees of the Company are appointed annually by the Company’s Board of Directors. The following individuals are the executive officers of the Company as of February 12, 2024:

Paul Beswick, age 49, is Senior Vice President and Global Chief Information Officer (CIO) of Marsh McLennan. In this role, he manages over 5,000 technologists supporting Marsh McLennan’s global businesses. Prior to his appointment as Marsh McLennan CIO in January 2021, Mr. Beswick was a Partner and Global Head of Oliver Wyman Labs and the Digital Practice at Oliver Wyman. During more than two decades with Oliver Wyman, he worked in various sectors, including retail, transportation, telecom, and consumer goods. Before this, Mr. Beswick headed Oliver Wyman's North American Retail Practice. Mr. Beswick holds an MA (first class) in chemical engineering from Cambridge University.

Katherine J. Brennan, age 45, is Senior Vice President and General Counsel of Marsh McLennan. In this role, she leads Marsh McLennan’s global legal, compliance and public affairs function, which supports the Company’s four businesses, Marsh, Guy Carpenter, Mercer and Oliver Wyman. She also leads the Company’s ESG efforts. Ms. Brennan has held several legal and compliance leadership roles at Marsh McLennan, serving most recently as General Counsel, Marsh LLC. She also served as Deputy General Counsel, Corporate Secretary and Chief Compliance Officer for Marsh McLennan from 2017 to 2021, and prior to that, as General Counsel of Guy Carpenter. Ms. Brennan currently serves on the Board of the Red Cross of Greater New York.

John Q. Doyle, age 60, is President and Chief Executive Officer of Marsh McLennan. Previously, from 2021 to 2022 he served as Group President and Chief Operating Officer, responsible for the strategy and operational objectives of Marsh McLennan’s four global businesses. He joined the firm in 2016 as President of Marsh, then led Marsh as President and CEO from 2017 to 2021. An industry veteran with more than 35 years of management experience, Mr. Doyle began his career at AIG, where he held several executive positions. He is a member of the Board of the New York Police and Fire Widows’ and Children’s Benefit Fund, a Trustee of the Inner-City Scholarship Fund, a member of the Board of Overseers of the Maurice R. Greenberg School of Risk Management, Insurance and Actuarial Science at St. John’s University and a former Director of the American Insurance Association. Mr. Doyle serves as the Chairman of the U.S. Federal Advisory Committee on Insurance.

Martine Ferland, age 62, is Chief Executive Officer of Mercer. She also serves as Vice Chair of Marsh McLennan. Prior to assuming her current role in March 2019, she was Mercer’s Group President, responsible for leading the firm’s regions and Global Business Solutions. She joined Mercer in 2011 as Retirement Business Leader for EMEA, and has served as Europe and Pacific Region President and Co-President, Global Health. Ms. Ferland began her career as a pension actuary and consultant at Willis Towers Watson, where she spent 25 years and held various leadership positions in Montreal and New York. Ms. Ferland is a Fellow of the Society of Actuaries and of the Canadian Institute of Actuaries and a member of the Board of Trustees of the New York Academy of Medicine.

Carmen Fernandez, age 50, is Senior Vice President and Chief People Officer for Marsh McLennan. Prior to her appointment as Chief People Officer in January 2021, Ms. Fernandez held positions within Marsh McLennan for 15 years, most recently Deputy CHRO, CHRO of Guy Carpenter, and HR leadership roles at Mercer, including North America HR Leader, Global HR Leader for the Career business and Chief of Staff in the Office of the CEO. Before joining Marsh McLennan, Ms. Fernandez worked in investment banking at Bank of America and Goldman Sachs. She began her career as a consultant with PricewaterhouseCoopers.

John Jones, age 52, is Chief Marketing and Communications officer of Marsh McLennan. Previously, he served as Chief Marketing and Communications Officer of Marsh from 2018 to 2022. Mr. Jones joined Marsh in 2016 as senior vice president of Marsh’s business planning, leading strategic planning and global growth initiatives. Prior to that, Mr. Jones was senior vice president of commercial marketing and strategy for AIG and has more than 25 years of marketing, communications and strategy experience.

Dean Klisura, age 60, is President and Chief Executive Officer of Guy Carpenter and serves as Vice Chair of Marsh McLennan. Prior to assuming this role in January 2022, he was President of Guy Carpenter, overseeing the North America, International, Specialty and Global Strategic Advisory business units. Prior to joining Guy Carpenter, Mr. Klisura was President of Marsh Global Placement and Advisory Services, leading property and casualty placement activities globally, as well as leading Bowring Marsh, the Insurer Consulting Group, and Marsh Advisory. He joined Marsh in 1993 and held several key global leadership roles including President of Global Specialties.

Mark McGivney, age 56, is Chief Financial Officer of Marsh McLennan. Prior to assuming this role in January 2016, Mr. McGivney held a number of senior financial management positions since joining the Company in 2007. Most recently he was Senior Vice President, Corporate Finance of Marsh McLennan, and was responsible for leading and directing the Company’s Corporate Development, Treasury and Investor Relations functions from 2014 until 2016. Prior to that, he served as Chief Financial Officer of Marsh, and Chief Financial Officer and Chief Operating Officer of Mercer. His prior experience includes senior positions at The Hanover Insurance Group, including serving as Senior Vice President of Finance, Treasurer, and Chief Financial Officer of the Property & Casualty business, as well as positions with Merrill Lynch and PricewaterhouseCoopers.

Martin South, age 59, is President and Chief Executive Officer of Marsh, a position he assumed in January 2022, and oversees all of Marsh’s businesses and operations globally. He also serves as Vice Chair of Marsh McLennan. With more than 30 years in the insurance industry, Mr. South joined Marsh for the first time in 1985 with Bowring Marsh, a Marsh McLennan broking unit. His industry experience includes senior leadership roles at Zurich Financial Services, where he was a member of the Group Management Board, responsible for all of Zurich’s operations outside of North America and Europe, and CEO of Zurich’s London operations. Since rejoining Marsh in 2007, Mr. South has served as CEO of Marsh’s Asia-Pacific region, CEO of Marsh UK and Ireland, CEO of Marsh Europe and CEO of Marsh U.S. and Canada.

Nicholas Studer, age 50, is Chief Executive Officer of Oliver Wyman Group, a role he assumed in July of 2021. He also serves as Vice Chair of Marsh McLennan. From 2017 to 2021, Mr. Studer was the Managing Partner of the Consumer, Industrial and Services Practice Group, before becoming Managing Partner of Oliver Wyman in 2021. He has held many senior positions at Oliver Wyman including Managing Partner of the Financial Services Practice Group, Head of the European Finance and Risk Practice and Global head of the Corporate and Institutional Banking practice. He has over 25 years of experience consulting in the UK, Continental Europe, and North America.

The Company is subject to the information reporting requirements of the Securities Exchange Act of 1934. In accordance with the Exchange Act, the Company files with, or furnishes to, the SEC its annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K and proxy statement for its annual shareholders' meeting. The Company makes these reports and any amendments to these reports available free of charge through its website, www.marshmclennan.com, as soon as reasonably practicable after they are filed with or furnished to the SEC. The SEC also maintains a website at www.sec.gov that contains reports, proxy and information statements and other information regarding issuers, like the Company, that file electronically with the SEC.

The Company also posts on its website certain governance and other information for investors.

The Company encourages investors to visit these websites from time to time, as information is updated and new information is posted. Website references in this report are provided as a convenience and do not constitute, and should not be viewed as, incorporation by reference of the information contained on, or available through, the websites. Therefore, such information should not be considered part of this report.