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FORM 10-K TABLE OF CONTENTS

SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, DC 20549

FORM 10-K

(Mark One)

For the Fiscal year ended December 31, 2002

OR

For the transition period from                                      to                                     

Commission File Number 001-13459

Affiliated Managers Group, Inc.
(Exact name of registrant as specified in its charter)

600 Hale Street, Prides Crossing, Massachusetts 01965
(Address of principal executive offices)

(617) 747-3300
(Registrant's telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

        Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ý    Noo

        Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of Registrant's knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this form 10-K. o

        Indicate by check mark whether the Registrant is an accelerated filer (as defined in Rule 12b-2 of the Act). Yes ý    Noo

        At June 28, 2002, the aggregate market value of the voting Common Stock held by non-affiliates of the Registrant, based upon the closing price of $61.50 on that date on the New York Stock Exchange, was $1,339,890,168. Calculation of holdings by non-affiliates is based upon the assumption, for these purposes only, that executive officers, directors and persons holding 10% or more of the Registrant's Common Stock are affiliates. There were 20,988,220 shares of the Registrant's Common Stock outstanding on March 25, 2003.

DOCUMENTS INCORPORATED BY REFERENCE

        Certain information called for by Part III of this report on Form 10-K is incorporated by reference from certain portions of the Proxy Statement of the Registrant to be filed pursuant to Regulation 14A and sent to stockholders in connection with the Annual Meeting of Stockholders to be held on June 3, 2003. Such Proxy Statement, except for the parts therein which have been specifically incorporated herein by reference, shall not be deemed "filed" as part of this report on Form 10-K.

FORM 10-K

TABLE OF CONTENTS

PART I

Item 1. Business

Overview

        We are an asset management company with equity investments in a diverse group of mid-sized investment management firms (our "Affiliates"). As of December 31, 2002, our affiliated investment management firms managed approximately $70.8 billion in assets across a broad range of investment styles and in three principal distribution channels: High Net Worth, Mutual Fund and Institutional. We pursue a growth strategy designed to generate shareholder value through the internal growth of our existing business across these three channels, in addition to investments in mid-sized investment firms and strategic transactions and relationships designed to enhance our Affiliates' businesses and growth prospects.

        In our investments in Affiliates, we typically hold a majority equity interest in each firm, with the remaining equity interests retained by the management of the Affiliate. Our investment approach addresses the succession and ownership transition issues facing the founders and principal owners of many mid-sized investment management firms by allowing them to preserve their firm's entrepreneurial culture and independence and to continue to participate in their firm's success. In particular, our structures are designed to:

•

maintain and enhance Affiliate managers' equity incentives in their firms;



•

preserve each Affiliate's distinct culture and investment focus; and



•

provide Affiliates with the ability to realize the benefits of scale economies in distribution, operations and technology.

        Although we invest in firms that we anticipate will grow independently and without our assistance, we are committed to helping Affiliates identify opportunities for growth and leverage the benefits of economies of scale. We assist our Affiliates by offering strategic support, broadening distribution channels and by developing new products and operational enhancements.

        We believe that a substantial number of opportunities to make investments in mid-sized investment management firms will continue to arise as their founders approach retirement age and begin to plan for succession. Our management identifies and develops relationships with promising potential firms based on a thorough understanding of the universe of such firms derived from our proprietary database that includes information from third party vendors, public and industry sources and our own research. Within our target universe, we seek the strongest and most stable firms with the best growth prospects, which are typically characterized by a strong multi-generational management team and culture of commitment to building a firm for its longer-term success, focused investment discipline and long-term investment track record, and diverse products and distribution channels.

Investment Management Operations

        Through our Affiliates, we provide more than 150 products across a broad range of asset classes and investment styles in three principal distribution channels: High Net Worth, Mutual Fund and Institutional. We believe that our diversification across asset classes, investment styles and distribution channels helps to mitigate our exposure to changing market environments.

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        A summary of selected financial data attributable to our operations follows:

(1)

Balances as of December 31.

(2)

Note 18 to the Consolidated Financial Statements describes the basis of presentation of our distribution channel operating results.

(3)

EBITDA represents earnings before interest expense, income taxes, depreciation and amortization. As a measure of liquidity, we believe that EBITDA is useful as an indicator of our ability to service debt, make new investments, meet working capital requirements and generate cash flow in each of our distribution channels. EBITDA is not a measure of liquidity under generally accepted accounting principles and should not be considered an alternative to cash flow from operations. EBITDA, as calculated by us, may not be consistent with computations of EBITDA by other companies. Our use of EBITDA, including a reconciliation to cash flow from operations, is discussed in greater detail in "Management's Discussion and Analysis of Financial Condition and Results of Operations." For purposes of our distribution channel operating results, holding company expenses have been allocated based on the proportion of aggregate cash flow distributions reported by each Affiliate in the particular distribution channel.

High Net Worth Distribution Channel

        Affiliate clients in the High Net Worth distribution channel include high net worth and affluent individuals, family trusts and managed accounts at brokerage firms and other sponsors that are attributable to individuals. Through our Affiliates, we provide customized investment management services for high net worth individuals and families through direct relationships, as well as through more than 90 managed account programs.

        Our two largest Affiliates (based on 2002 EBITDA) in the High Net Worth distribution channel are:

•

Rorer Asset Management, LLC ("Rorer"), a Philadelphia-based investment adviser that employs a disciplined relative value investment process in managing equity portfolios; and

2

•

Tweedy, Browne Company LLC ("Tweedy, Browne"), a New York-based investment adviser that employs a value-oriented investment approach advocated by Benjamin Graham to invest in global and domestic securities.

        In addition, Welch & Forbes LLC, based in Boston, and Gofen and Glossberg, L.L.C., based in Chicago, are investment counseling firms that provide customized investment advisory and fiduciary services to a range of clients including personal trust, high net worth families and charitable foundations.

        In 2002 and in the beginning of 2003, we undertook several initiatives to assist our Affiliates with High Net Worth distribution. In January 2002, we launched our first multi-Affiliate product, known as Multiple Attribute Portfolios (or "MAPs"), that allows sponsors to offer investors a series of portfolios, each managed by multiple independent Affiliates that employ separate and distinct investment styles. Together, the portfolios create a spectrum of asset, style and risk allocations designed to meet the investment goals of a wide range of separate account investors and provide investors an opportunity to access a diverse group of independently managed products in a single account, at a reasonable asset level. The product is currently marketed through networks of registered representatives at various national financial services institutions.

        In January 2003, we announced the formation of the Portfolio Services Group ("PSG") division of The Burridge Group LLC ("Burridge"), a Chicago-based Affiliate. PSG was developed as a platform to distribute single and multi-manager separate account products sold through brokerage firms and banks. PSG is presently distributing investment management products for the two other divisions of Burridge (Burridge Growth Partners and Sound Capital Partners), as well as selected products managed by three other Affiliates within our High Net Worth distribution channel, Essex Investment Management Company, LLC ("Essex"), Frontier Capital Management Company, LLC ("Frontier") and The Renaissance Group LLC ("Renaissance"). In addition, PSG works with various national financial services institutions to distribute MAPs.

Mutual Fund Distribution Channel

        Through our Affiliates, we provide advisory or sub-advisory services to 36 domestic and offshore mutual funds. These funds are distributed to retail and institutional clients directly and through intermediaries, including independent investment advisers, retirement plan sponsors, broker-dealers, major fund marketplaces and bank trust departments.

        Our two largest Affiliates (based on 2002 EBITDA) in the Mutual Fund distribution channel are:

•

Tweedy, Browne, which advises the Tweedy, Browne Global Value Fund and the Tweedy, Browne American Value Fund, which are two domestic mutual funds, as well as certain offshore funds; and



•

Friess Associates, LLC ("Friess"), a Delaware, Wyoming and Arizona-based adviser to three growth equity mutual funds—the Brandywine Fund, Brandywine Advisers Fund and Brandywine Blue Fund.

        In addition, Third Avenue Management LLC ("Third Avenue") and The Managers Funds LLC ("Managers"), each described in further detail below, focus on providing investment management services in the Mutual Fund distribution channel.

        In August 2002, we completed our most recent investment in the Mutual Fund distribution channel by acquiring a 60% interest in Third Avenue. The remaining 40% of the business is held by a broad group of Third Avenue's management team. Third Avenue is a New York-based investment manager that serves as the adviser to the Third Avenue family of no-load value mutual funds, including the flagship Third Avenue Value Fund, and as the sub-adviser to non-proprietary mutual funds and

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annuities. Third Avenue employs a deep value approach to investing in equities and real estate and corporate debt securities.

        Managers is a Norwalk, Connecticut-based adviser to two families of no-load mutual funds, The Managers Funds and Managers AMG Funds. We acquired Managers in 1999 to expand our business in the Mutual Fund distribution channel, and to support the growth and operations of our Affiliates by providing them a cost-effective way to access the Mutual Fund distribution channel. With Managers and our Affiliates, we formed Managers AMG Funds, a no-load mutual fund family sub-advised by several of our Affiliates and distributed to retail and institutional clients directly by Managers and through intermediaries. The Managers AMG fund family continued to grow in 2002 with the addition of funds managed by Systematic Financial Management, L.P. and Burridge.

Institutional Distribution Channel

        Through our Affiliates, we offer investment products across more than 20 different investment styles in the Institutional distribution channel, including small, small/mid, mid and large capitalization value and growth equity. Through this distribution channel, we manage assets for foundations and endowments, defined benefit and defined contribution plans for corporations and municipalities and Taft-Hartley plans.

        Our two largest Affiliates (based on 2002 EBITDA) in the Institutional distribution channel are:

•

Essex, a Boston-based investment adviser that specializes in growth equity portfolios and employs fundamental research combined with active portfolio management; and



•

Tweedy, Browne.

        In 2002, we continued working closely with our Affiliates in executing and enhancing their institutional marketing and client service initiatives. Our efforts are designed to ensure that their products and services successfully address the competitive demands of the marketplace. Specifically, we provide our Affiliates with resources to improve sales and marketing materials, network with the pension consultant and plan sponsor communities, and establish new distribution alternatives. These resources provide our Affiliates the opportunity to tailor appropriate calling programs in each segment of the Institutional distribution channel.

Our Structure and Relationship with Affiliates

        While we operate our business through our Affiliates in our three principal distribution channels, we strive to maintain each Affiliate's entrepreneurial culture and independence through our investment structure. Our principal investment structure involves the ownership of a majority interest in our Affiliates, with each Affiliate organized as a separate firm. Each Affiliate operating agreement is tailored to meet that Affiliate's particular characteristics and provides us the authority to cause or prevent certain actions to protect our interests.

        We have revenue sharing arrangements with most of our Affiliates. Under these arrangements, a percentage of revenue (or in certain cases different percentages relating to the various sources or amounts of revenue of a particular Affiliate) is allocated for use by management of that Affiliate in paying operating expenses of the Affiliate, including salaries and bonuses. We call this the "Operating Allocation." The remaining portion of the Affiliate's revenue is allocated to the owners of that Affiliate (including us), and called the "Owners' Allocation." Each Affiliate distributes its Owners' Allocation to its managers and to us generally in proportion to their and our respective ownership interests in that Affiliate although, as discussed below, in certain circumstances we may permit an Affiliate's management to use its portion of the Owners' Allocation to meet the Affiliate's operating expenses.

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        We only agree to a particular revenue sharing arrangement if we believe that the Operating Allocation will cover operating expenses of the Affiliate, including a potential increase in expenses or decrease in revenue without a corresponding decrease in operating expenses. To the extent that we are unable to anticipate changes in the revenue and expense base of an Affiliate, the agreed-upon Operating Allocation may not be large enough to pay for all of the Affiliate's operating expenses. The allocations and distributions of cash to us under the Owners' Allocation generally have priority over the allocations and distributions to the Affiliate's managers, which help to protect us if there are any expenses in excess of the Operating Allocation of the Affiliate. Thus, if an Affiliate's expenses exceed its Operating Allocation, the excess expenses first reduce the portion of the Owners' Allocation allocated to the Affiliate's managers until that portion is eliminated, and then reduce the portion allocated to us. Any such reduction in our portion of the Owners' Allocation is required to be paid back to us out of the portion of future Owners' Allocation allocated to the Affiliate's managers. Nevertheless, we may agree to adjustments to revenue sharing arrangements to accommodate our business needs or those of our Affiliates, including deferring or forgoing the receipt of some portion or all of our share of an Affiliate's revenue to permit the Affiliate to fund operating expenses or restructuring our relationship with an Affiliate, if we believe that doing so will maximize the long-term benefits to us. In addition, a revenue sharing arrangement may be modified to a profit-based arrangement (as described below) to better accommodate our business needs or those of our Affiliates.

        One of the purposes of our revenue sharing arrangements is to provide ongoing incentives for Affiliate managers by allowing them:

•

to participate in the growth of their firm's revenue, which may increase their compensation from the Operating Allocation, and their distributions from the Owners' Allocation; and



•

to control operating expenses, thereby increasing the portion of the Operating Allocation which is available for growth initiatives and compensation.

        An Affiliate's managers therefore have incentives to increase revenue (thereby increasing the Operating Allocation and their share of the Owners' Allocation) and to control expenses (thereby increasing the amount of Operating Allocation available for their compensation).

        Some of our Affiliates are not subject to a revenue sharing arrangement, but instead operate on a profit-based model similar to a wholly-owned subsidiary. In our profit-based Affiliates, we participate in a budgeting process with the Affiliate and receive as cash flow a share of its profits. As a result, we participate fully in any increase or decrease in the revenue or expenses of such firms. In those cases, we generally provide incentives to management through compensation arrangements based on the performance of the Affiliate. Currently, our profit-based Affiliates account for less than 10% of our EBITDA.

Our Purchase of Additional Interests in Our Existing Affiliates

        In our investment structures, the management team at each Affiliate retains an equity interest in that Affiliate. We consider this a key way that we provide our Affiliates' managers with incentives to grow their firms as well as align their interests with ours. In order to further increase these incentives, we include in the organizational documents of each Affiliate "put" rights for its managers. The put rights require us, from time to time and at the request of an Affiliate's manager, to buy portions of his or her interests in the Affiliate. In this way, an Affiliate's managers can realize a portion of the equity value that they have created in their firm. In addition, organizational documents of some of our Affiliates provide us with "call" rights that permit us to require an Affiliate's managers to sell us portions of their interests in the Affiliate. Finally, the organizational documents of each Affiliate include provisions obligating each manager to sell his or her remaining interests to us at a point in the future, generally after the termination of his or her employment. The purchase price for these transactions is generally based on a multiple of the Affiliate's Owners' Allocation at the time the right

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is exercised, which is intended to represent the fair value of the equity. We pay for these purchases in cash, shares of our Common Stock or other forms of consideration. Underlying these provisions is our basic philosophy that the managers of each Affiliate should maintain an ownership level in that Affiliate within a range that offers them sufficient incentives to grow and improve their business to create equity value for themselves.

        The put rights are designed to permit the managers of an Affiliate to sell portions of their retained ownership to us. Instead of our purchase of a manager's interest in the Affiliate occurring only in the event of the termination of his or her employment, the put rights are designed to result in our purchase of additional interests in our Affiliates at a more gradual rate. We believe that our more gradual purchase of interests in Affiliates will enhance our ability to keep our ownership of each Affiliate within a desired range. We intend to continue providing equity participation opportunities in our Affiliates to more junior members of their management as well as to key employees.

        In most cases, the put rights do not become exercisable for a period of several years from the date of our investment in an Affiliate. Once exercisable, the put rights generally are limited in the aggregate to a percentage of a manager's ownership interest. The most common formulation among the Affiliates is that a manager's put rights:

•

do not commence until five years after the date of our investment (or, if later, the date he or she purchased his or her interest in the Affiliate);



•

are limited, in the aggregate, to 50% of his or her interests in the Affiliate; and



•

are limited, in any 12-month period, to 10% of the greatest interest he or she held in the Affiliate.

        In addition, the organizational documents of the Affiliates often contain a limitation on the maximum total amount that management of any Affiliate may require us to purchase pursuant to their put rights in any 12-month period. Our current estimates of our financial obligations pursuant to our Affiliates' managers' put rights are presented in "Management's Discussion and Analysis of Financial Condition and Results of Operations."

        Call rights are designed to provide a procedure for us and the managers of some of our Affiliates to facilitate a transition within the senior management team after an agreed-upon period of time. The call rights vary in each specific instance, but in all cases the timing and procedure are agreed upon when we make our investment.

        The organizational documents of the Affiliates generally provide that an Affiliate's managers will realize the remaining equity value that they have created following the termination of their employment with the Affiliate. In general, upon a manager's retirement after an agreed-upon number of years, or upon his or her earlier death, permanent incapacity or termination without cause (but with our consent), he or she is required to sell to us (and we are required to purchase) his or her remaining interests. If an Affiliate collects any key-man life insurance or lump-sum disability insurance proceeds upon the death or permanent incapacity of a manager, the Affiliate generally must use that money to purchase that manager's interests. The purchase of interests by an Affiliate would have the effect of ratably increasing our ownership percentage as well as that of each of its remaining managers. By contrast, the purchase of interests by us only increases our ownership percentage.

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Diversification of Assets under Management and EBITDA

        The following table provides information regarding the composition of our assets under management and EBITDA for the year ended December 31, 2002.

(1)

The definition of EBITDA is presented in Note (3) on page 2. Our use of EBITDA, including a reconciliation to cash flow from operations, is discussed in greater detail in "Management's Discussion and Analysis of Financial Condition and Results of Operations." EBITDA amounts are pro forma to include our investment in Third Avenue as if it occurred on January 1, 2002. Our investment in Third Avenue closed in the third quarter of 2002.

Industry

        The asset management industry is an important segment of the financial services industry in North America and has been a key driver of growth in financial services over the last decade. As of the end of 2001 (the most recently compiled industry data), the assets under management across our principal distribution channels totaled more than $30 trillion. While the aggregate value of assets managed by the industry has been reduced by equity market declines since that time, we believe prospects for overall industry growth (estimated by one industry consultant to increase at a rate of 7.5% annually over the next five years) remain strong. We expect that this growth will be driven by market-related increases in assets under management, broad demographic trends and wealth creation related to growth in gross domestic product, and will be experienced in varying degrees across all three of the principal distribution channels for our Affiliates' products: High Net Worth, Mutual Fund and Institutional.

        In the High Net Worth distribution channel (comprised of high net worth and affluent individuals, family trusts and managed accounts), we believe that each of the three factors of market performance, demographics and gross domestic product growth will lead to asset growth. High net worth individuals (those having more than $1 million in investable assets) represent the primary component of this distribution channel. At the end of 2001, there were an estimated 2.2 million high net worth individuals, with aggregate assets of $7.6 trillion. One recent industry report forecasts this asset base to grow to a total of $11.2 trillion by the end of 2006, an annual growth rate of 8%. We also expect that assets in the High Net Worth distribution channel will grow as a result of recent innovations in product development and distribution that allow a growing number of affluent investors access to managed account products at lower investment levels than has been traditionally available.

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        In the Mutual Fund distribution channel, the Investment Company Institute reports that more than 93 million individuals in almost 55 million households in the United States are invested in mutual funds, representing a 98% penetration level in U.S. households with more than $20,000 in investable assets. In 2002, net inflows to mutual funds (excluding money market funds) totaled approximately $122 billion. Despite positive flows, aggregate mutual fund assets declined from $7 trillion at the end of 2001 to $6.4 trillion at the end of 2002, principally as a result of market declines. We anticipate that inflows to mutual funds will continue and that aggregate mutual fund assets, particularly those in equity mutual funds, will increase in line with longer-term market growth.

        The substantial majority of assets in the Institutional distribution channel are in retirement plans, and, to a lesser extent, endowments and foundations. Recent industry data indicates that aggregate pension assets totaled nearly $9 trillion at the end of 2001. While growth in Institutional retirement plans has slowed in recent years, we anticipate that the combination of an aging work force, higher funding levels to pension plans that are deemed under-funded and longer-term market growth should contribute to the ongoing strength of this distribution channel.

Investment Advisers

        Our principal targeted size range for prospective Affiliates is $500 million to $20 billion of assets under management. Within this size range, we have identified more than 1,450 investment management firms in the United States, Canada and the United Kingdom. We believe that, in the coming years, a substantial number of investment opportunities will arise as founders of such firms approach retirement age and begin to plan for succession. We also anticipate that there will be significant additional investment opportunities among firms that are currently wholly owned by larger entities. We believe that we are well positioned to take advantage of these investment opportunities because we have a management team with substantial industry experience and expertise in structuring and negotiating transactions, and an organized process for identifying and contacting investment prospects.

Competition

        In each of our three principal distribution channels, we and our Affiliates compete with a large number of domestic and foreign investment management firms, including public companies, subsidiaries of commercial and investment banks and insurance companies. In comparison to us and our Affiliates, these firms generally have greater resources and assets under management, and many offer a broader array of investment products and services. Since certain Affiliates are active in the same distribution channels, from time to time they compete with each other for clients. In addition, there are relatively few barriers to entry by new investment management firms, especially in the Institutional distribution channel. We believe that the most important factors affecting our and our Affiliates' ability to compete for clients in our three principal distribution channels are:

•

the products offered;



•

the abilities, performance records and reputation of the Affiliates and their management teams;



•

the management fees charged;



•

the level of client service offered; and



•

the development of new investment strategies and the marketing of such strategies.

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        The relative importance of each of these factors can vary depending on the distribution channel and the type of investment management service involved. Each Affiliate's ability to retain and increase assets under management would be adversely affected if client accounts underperform in comparison to relevant benchmarks or peer groups, or if key personnel leave the Affiliate. The ability of each Affiliate to compete with other investment management firms also depends, in part, on the relative attractiveness of its investment philosophies and methods under then-prevailing market conditions.

        A component of our growth strategy is the acquisition of equity interests in additional mid-sized investment management firms. In seeking to make such acquisitions, we compete with many acquirers of investment management firms, including other investment management holding companies, insurance companies, broker-dealers, banks and private equity firms. Many of these companies have longer operating histories and greater resources than we do, which may make them more attractive to the owners of firms in which we are considering an investment and may enable them to offer greater consideration to such owners. We believe that important factors affecting our ability to compete for future investments are:

•

the degree to which target firms view our investment structure as preferable, financially and operationally, to acquisition or investment arrangements offered by other potential purchasers; and

•

the reputation and performance of our existing and future Affiliates, by which target firms may judge us and our future prospects.

Government Regulation

        Our Affiliates' businesses are highly regulated, primarily by U.S. federal authorities and to a lesser extent by other authorities, including non-U.S. authorities. The failure of our Affiliates to comply with laws or regulations could result in fines, suspensions of individual employees or other sanctions, including revocation of an Affiliate's registration as an investment adviser, commodity trading advisor or broker-dealer. Each of our Affiliates is registered as an investment adviser with the Securities and Exchange Commission under the Investment Advisers Act of 1940, as amended (the "Investment Advisers Act"), and is subject to the provisions of the Investment Advisers Act and related regulations. The Investment Advisers Act requires registered investment advisers to comply with numerous obligations, including record keeping requirements, operational procedures and disclosure obligations. We do not directly engage in the business of providing investment advice and therefore are not registered as an investment adviser. Our Affiliates are also subject to regulation under the securities and fiduciary laws of various states. Moreover, many of our Affiliates act as advisers or sub-advisers to mutual funds, which are registered as investment companies with the Securities and Exchange Commission pursuant to the Investment Company Act of 1940, as amended (the "1940 Act"). As an adviser or sub-adviser to a registered investment company, each of these Affiliates must comply with the requirements of the 1940 Act and related regulations. In addition, an adviser or sub-adviser to a registered investment company generally has obligations with respect to the qualification of the registered investment company under the Internal Revenue Code of 1986, as amended (the "Code").

        Our Affiliates are also subject to the Employee Retirement Income Security Act of 1974, as amended ("ERISA"), and related regulations, to the extent they are "fiduciaries" under ERISA with respect to some of their clients. ERISA and related provisions of the Code impose duties on persons who are fiduciaries under ERISA, and prohibit certain transactions involving the assets of each ERISA plan that is a client of an Affiliate, as well as certain transactions by the fiduciaries (and several other related parties) to such plans. One of our Affiliates, First Quadrant, L.P., is also registered with the Commodity Futures Trading Commission as a commodity trading advisor and is a member of the National Futures Association. Finally, Tweedy, Browne, a subsidiary of Managers and an affiliate of Third Avenue are registered under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), as broker-dealers and, therefore, are subject to extensive regulation relating to sales methods,

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trading practices, the use and safekeeping of customers' funds and securities, capital structure, record keeping and the conduct of directors, officers and employees.

        Furthermore, the Investment Advisers Act and the 1940 Act provide that each investment management contract under which our Affiliates manage assets for other parties either terminates automatically if assigned, or states that it is not assignable without consent. In general, the term "assignment" includes not only direct assignments, but also indirect assignments which may be deemed to occur upon the direct or indirect transfer of a "controlling block" of our voting securities or the voting securities of one of our Affiliates. The 1940 Act further provides that all investment contracts with mutual fund clients may be terminated by such clients, without penalty, upon no later than 60 days' notice.

        Several of our affiliated investment management firms are also subject to the laws of non-U.S. jurisdictions and non-U.S. regulatory agencies. For example, First Quadrant Limited, located in London, is regulated by the Financial Services Authority of the United Kingdom, and some of our other affiliated investment management organizations are investment advisers to funds which are organized under non-U.S. jurisdictions, including Luxembourg (where the funds are regulated by the Institute Monetaire Luxembourgeois), Bermuda (where the funds are regulated by the Bermuda Monetary Authority) and Ireland (where the funds are regulated by the Central Bank of Ireland). In addition, DFD Select Group, N.V. distributes funds (some which are managed by our Affiliates) in a variety of foreign jurisdictions. DFD Select Group, N.V. and any of our affiliated investment management firms that manage such funds are therefore subject to the securities laws governing the investment management and distribution of such funds in the applicable jurisdictions.

        The foregoing laws and regulations generally grant supervisory agencies and bodies broad administrative powers, including the power to limit or restrict any of the Affiliates from conducting their business in the event that they fail to comply with such laws and regulations. Possible sanctions that may be imposed in the event of such noncompliance include the suspension of individual employees, limitations on the Affiliate's business activities for specified periods of time, revocation of the Affiliate's registration as an investment adviser, commodity trading advisor, broker-dealer and/or other registrations, and other censures and fines. Changes in these laws or regulations could have a material adverse impact on our profitability and mode of operations.

        Our officers, directors and employees and the officers and employees of each of the Affiliates may own securities that are also owned by one or more of the Affiliates' clients. We and each Affiliate have internal policies with respect to individual investments that require reports of certain securities transactions and restrict certain transactions so as to minimize possible conflicts of interest.

Employees and Corporate Organization

        As of December 31, 2002, we had 46 employees and our Affiliates employed approximately 803 persons. Approximately 777 of these 849 employees were full-time employees. Neither we nor any of our Affiliates is subject to any collective bargaining agreements, and we believe that our labor relations are good. We were formed in 1993 as a corporation under the laws of the State of Delaware.

Corporate Liability and Insurance

        Our Affiliates' operations entail the inherent risk of liability related to litigation from clients and actions taken by regulatory agencies. In addition, we face liability both directly as a control person of our Affiliates, and indirectly as a general partner or manager member of certain of our Affiliates. To protect our overall operations from such liability, we maintain errors and omissions and general liability insurance in amounts which we and our Affiliates consider appropriate. There can be no assurance, however, that a claim or claims will not exceed the limits of available insurance coverage, that any insurer will remain solvent and will meet its obligations to provide coverage, or that such coverage will

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continue to be available with sufficient limits or at a reasonable cost. A judgment against one of our Affiliates in excess of available coverage could have a material adverse effect on us.

Cautionary Statements

Declines in the equity markets adversely affect our performance.

        Our Affiliates' investment management contracts typically provide for payment based on the market value of assets under management, and payments will be adversely affected by declines in the equity markets. In addition, certain of our Affiliates' investment management contracts include fees based on investment performance, which are directly dependent upon investment results and thus often vary substantially from year to year. Unfavorable market performance, fluctuations in the prices of specific securities, asset withdrawals or other changes in the investment patterns of our Affiliates' clients may reduce our Affiliates' assets under management, which in turn may adversely affect the fees payable to our Affiliates and, ultimately, our consolidated results of operations and financial condition.

Our growth strategy depends upon continued growth from our existing Affiliates and upon our making new investments in mid-sized investment management firms.

        Our Affiliates may not be able to maintain their respective levels of performance or contribute to our growth at their historical levels. Also, our Affiliates may be unable to carry out their management succession plans, which may adversely affect their operations and revenue streams.

        The success of our investment program will depend upon our ability to find suitable firms in which to invest and our ability to negotiate agreements with such firms on acceptable terms. We cannot be certain that we will be successful in finding or investing in such firms or that they will have favorable operating results following our investment, which could have an adverse effect on our business, financial condition and results of operations.

The failure to receive regular distributions from our Affiliates would adversely affect us, and our holding company structure results in substantial structural subordination and may affect our ability to make payments on our obligations.

        Because we are a holding company, we receive substantially all of our cash from distributions made to us by our Affiliates. An Affiliate's payment of distributions to us may be subject to claims by the Affiliate's creditors and to limitations applicable to the Affiliate under federal and state laws, including securities and bankruptcy laws. Additionally, an Affiliate may default on some or all of the distributions that are payable to us. As a result, we cannot guarantee that we will always receive these distributions from our Affiliates. The failure to receive the distributions to which we are entitled under our agreements with our Affiliates would adversely affect us, and may affect our ability to make payments on our obligations.

        Our right to receive any assets of our Affiliates or subsidiaries upon their liquidation or reorganization, and thus the right of the holders of securities issued by us to participate in those assets, typically would be subordinated to the claims of that entity's creditors. In addition, even if we were a creditor of any of our Affiliates or subsidiaries, our rights as a creditor would be subordinate to any security interest and indebtedness that is senior to us.

The agreed-upon expense allocation under our revenue sharing arrangements with Affiliates may not be large enough to pay for all of that Affiliate's operating expenses.

        Our Affiliates have generally entered into agreements with us under which they have agreed to pay us a specified percentage of their gross revenue, while retaining a percentage of revenue for use in paying that Affiliate's operating expenses. We may not anticipate and reflect in those agreements possible changes in the revenue and expense base of any Affiliate, and the agreed-upon expense allocation may not be large enough to pay for all of an Affiliate's operating expenses. We may elect to

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defer the receipt of our share of an Affiliate's revenue to permit the Affiliate to fund such operating expenses, or we may restructure our relationship with an Affiliate with the aim of maximizing the long-term benefits to us, but we cannot be certain that any such deferral or restructured relationship would be of any greater benefit to us. Such a deferral or restructured relationship might have an adverse affect on our near-term or long-term profitability and financial condition.

We expect that we will need to raise additional capital in the future, and existing or future resources may not be available to us in sufficient amounts or on acceptable terms.

        While we believe that our existing cash resources and cash flow from operations will be sufficient to meet our working capital needs for normal operations for the foreseeable future, our continuing acquisitions of interests in new affiliated investment management firms will require additional capital. We may also need to repurchase some or all of our outstanding zero coupon senior convertible notes and floating rate senior convertible securities on various dates, the next of which is May 7, 2004, and we have obligations to purchase additional equity in existing Affiliates, which obligations will be triggered from time to time. These obligations may require more cash than is available from operations. Thus, we may need to raise capital by making additional borrowings or by selling shares of our Common Stock or other equity or debt securities, or to otherwise refinance a portion of these obligations. These financing activities could increase our interest expense, decrease our Net Income and dilute the interests of our existing stockholders. Moreover, we may not be able to obtain such financing on acceptable terms, if at all.

        Repurchase Obligations under Zero Coupon Senior Convertible Notes and under Floating Rate Senior Convertible Securities.    In May 2001, we issued $251 million aggregate principal amount at maturity of zero coupon senior convertible notes due 2021. Subsequent to December 31, 2002, we repurchased $111.5 million principal amount at maturity of the zero coupon senior convertible notes in privately negotiated transactions. On May 7th of 2004, 2006, 2011 and 2016, holders may require us to repurchase all or a portion of these notes at their accreted value. In February 2003, we issued $300 million of floating rate senior convertible securities due 2033. The holders of the convertible securities may require us to repurchase such securities on February 25 of 2008, 2013, 2018, 2023 and 2028, at their principal amount. While we cannot predict whether or when holders of the notes or the convertible securities will choose to exercise their repurchase rights, we believe that they would become more likely to do so in the event that the price of our Common Stock does not exceed certain levels or if interest rates increase, or both. We may choose to pay the purchase price in cash or (subject to certain conditions) in shares of our Common Stock, or in a combination of both. We may wish to avoid paying the purchase price in Common Stock if we believe that doing so would be unfavorable. We currently intend to pay the repurchase price for the notes and the convertible securities with cash. Therefore, if a substantial portion of the notes or the convertible securities were to be submitted for repurchase on any of the repurchase dates, we might need to use a substantial amount of our available sources of liquidity for this purpose. This could have the effect of restricting our ability to fund new acquisitions or to meet other future working capital needs, as well as increasing our costs of borrowing. We may seek other means of refinancing or restructuring our obligations under the notes or the convertible securities, but this may result in terms less favorable than those under the existing notes or convertible securities.

        Obligations to Purchase Additional Equity in Our Affiliates.    Under our agreements with our Affiliates, we typically are obligated to purchase additional ownership interests in our Affiliates from their managers in certain circumstances. The price for these purchases may, in certain cases, be substantial and may result in us having more interest expense and less Net Income. These purchases will also result in our ownership of larger portions of our Affiliates, which may have an adverse effect on our cash flow and liquidity. In addition, in connection with these purchases, we may face the financing risks described above.

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        Revolving Credit Facility.    We currently have a revolving credit facility under which we had no debt outstanding as of December 31, 2002 and the ability to borrow up to $250 million. Subject to the agreement of the lenders (or prospective lenders) in the facility to increase commitments, we have the option to increase the facility to $350 million. We have used our credit facilities in the past, and we may do so again in the future, to fund investments in new and existing Affiliates, and we also may use the credit facility for working capital purposes or to refinance other indebtedness.

        Our credit facility matures in August 2005. While we intend to obtain a new credit facility prior to that time, we may not be able to obtain this financing on terms comparable to our current credit facility. Our failure to do so could increase our interest expense, decrease our Net Income and adversely affect our ability to fund new investments and otherwise use our credit facility as described above.

        We may borrow under our credit facility only if we continue to meet certain financial tests, including interest and leverage ratios. In addition, our credit facility contains provisions for the benefit of our lenders that restrict the manner in which we can conduct our business, that may adversely affect our ability to make investments in new and existing Affiliates and that may have an adverse impact on the interests of our stockholders.

        Because indebtedness under our credit facility bears interest at variable rates, increases in interest rates may increase our interest expense, which could adversely affect our cash flow, our ability to meet our debt service obligations and our ability to fund future investments. Although from time to time we are party to interest rate hedging contracts designed to offset a portion of our exposure to interest rate fluctuations, we cannot be certain that this strategy will be effective.

We have substantial intangibles on our balance sheet, and any re-valuation of our intangibles could adversely affect our results of operations and financial position.

        At December 31, 2002, our total assets were $1.2 billion, of which $1.1 billion (or approximately 90%) were intangible assets consisting of acquired client relationships and goodwill. We cannot be certain that we will ever realize the value of such intangible assets. We are amortizing, or writing off, acquired client relationships with definite lives over a weighted average period of 16 years. Historically, we have also amortized goodwill and certain other intangible assets, but have ceased to do so as a result of recent accounting rule changes.

        Under Financial Accounting Standard No. 142 ("FAS 142"), "Goodwill and Other Intangible Assets" (which generally became effective January 1, 2002), goodwill and other intangible assets that have indefinite lives are no longer amortized but are instead tested for impairment using a new fair value impairment test. Since the fair value test is more rigorous than the undiscounted cash flow methodology that companies previously used, companies that have intangible assets (including us) are now more likely to incur impairment charges.

We and our Affiliates rely on certain key personnel and cannot guarantee their continued service.

        We depend on the efforts of our executive officers and our other officers and employees. Our executive officers, in particular, play an important role in the stability and growth of our existing Affiliates and in identifying potential investment opportunities for us. Our officers do not have employment agreements with us, although each of them has a significant equity interest in us, including stock options subject to vesting provisions.

        In addition, our Affiliates depend heavily on the services of key principals, who in many cases have managed their firms for many years. These principals often are primarily responsible for their firm's investment decisions. Although we use a combination of economic incentives, vesting provisions and, in some instances, non-solicitation agreements and employment agreements in an effort to retain key management personnel, there is no guarantee that these principals will remain with their firms.

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Moreover, since certain Affiliates contribute significantly to our revenue, the loss of key management personnel at these Affiliates could have a disproportionate impact on our business.

        The loss of key management personnel or an inability to attract, retain and motivate sufficient numbers of qualified management personnel may adversely affect our business and our Affiliates' businesses. The market for investment managers is extremely competitive and is increasingly characterized by the frequent movement of investment managers among different firms. In addition, since individual investment managers at our Affiliates often maintain a strong, personal relationship with their clients that is based on their clients' trust in the manager, the departure of a manager could cause the Affiliate to lose client accounts, which could have a material adverse effect on the results of operations and financial condition of both the Affiliate and us.

Our Affiliates' investment management contracts are subject to termination on short notice.

        Our Affiliates derive almost all of their revenue from their clients based upon their investment management contracts with those clients. These contracts are typically terminable by the client without penalty upon relatively short notice (typically not longer than 60 days). We cannot be certain that our Affiliates will be able to retain their existing clients or to attract new clients. If our Affiliates' clients withdraw a substantial amount of funds, it is likely to harm our results.

Our industry is highly competitive.

        Through our Affiliates, we compete with a broad range of investment managers, including public and private investment advisers, firms associated with securities broker-dealers, banks, insurance companies and other entities that serve our three principal distribution channels, all of whom may have greater resources. This competition may reduce the fees that our Affiliates can obtain for their services. We believe that our Affiliates' ability to compete effectively with other firms in our three distribution channels depends upon our Affiliates' products, investment performance and client-servicing capabilities, and the marketing and distribution of their investment products. Our Affiliates may not compare favorably with their competitors in any or all of these categories. From time to time, our Affiliates also compete with each other for clients.

        The market for acquisitions of interests in investment management firms is highly competitive. Many other public and private financial services companies, including commercial and investment banks, insurance companies and investment management firms, which have significantly greater resources than we do, also invest in or buy investment management firms. We cannot guarantee that we will be able to compete effectively with such companies, that new competitors will not enter the market or that such competition will not make it more difficult or not feasible for us to make new investments in investment management firms.

Our Affiliates' businesses are highly regulated.

        Many aspects of our Affiliates' businesses are subject to extensive regulation by various U.S. federal regulatory authorities, certain state regulatory authorities and non-U.S. regulatory authorities. We cannot ensure that our Affiliates will fulfill all applicable regulatory requirements. The failure of any Affiliate to satisfy regulatory requirements could subject that Affiliate to sanctions that might materially impact the Affiliate's business and our business.

Our Affiliates' autonomy limits our ability to alter their management practices and policies, and we may be held responsible for liabilities incurred by them.

        Although our agreements with our Affiliates typically give us the authority to control and/or vote with respect to certain of their business activities, most of our Affiliates manage their own day-to-day operations, including investment management policies and fee levels, product development, client relationships, compensation programs and compliance activities. As a result, we may not become aware, for example, of an Affiliate's loss of a significant client or an Affiliate's non-compliance with a

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regulatory requirement as quickly as if we were involved in the day-to-day business of the Affiliate, and we may not become aware of such event at all. As a consequence, our financial condition and results of operations may be adversely affected by problems stemming from the day-to-day operations of our Affiliates.

        Some of our Affiliates are partnerships of which we are, or an entity controlled by us is, the general partner. Consequently, to the extent that any of these Affiliates incurs liabilities or expenses that exceed its ability to pay for them, we may be directly or indirectly liable for their payment. In addition, with respect to each of our Affiliates, we may be held liable in some circumstances as a control person for the acts of the Affiliate or its employees. While we and our Affiliates maintain errors and omissions and general liability insurance in amounts believed to be adequate to cover certain potential liabilities, we cannot be certain that we will not have claims that exceed the limits of our available insurance coverage, that our insurers will remain solvent and will meet their obligations to provide coverage or that insurance coverage will continue to be available to us with sufficient limits and at a reasonable cost. A judgment against any of our Affiliates and/or us in excess of available insurance coverage could have a material adverse effect on the Affiliate and/or us.

Our Affiliates' international operations are subject to foreign risks, including political, regulatory, economic and currency risks.

        Some of our Affiliates operate or advise clients outside of the United States, and one affiliated investment management firm, DFD Select Group, N.V., is based outside the United States. Accordingly, we and our affiliated investment management firms that have foreign operations are subject to risks inherent in doing business internationally, which risks may include changes in applicable laws and regulatory requirements, difficulties in staffing and managing foreign operations, longer payment cycles, difficulties in collecting investment advisory fees receivable, less stringent legal, regulatory and accounting regimes, political instability, fluctuations in currency exchange rates, expatriation controls, expropriation risks and potential adverse tax consequences. These or other foreign risks may have an adverse effect both on our Affiliates and on our consolidated business, financial condition and results of operations.

The price of our Common Stock historically has been volatile, and the sale of substantial amounts of our Common Stock could adversely impact the price of our Common Stock.

        The market price of our Common Stock historically has experienced and may continue to experience high volatility, and the broader stock market has experienced significant price and volume fluctuations in recent years. This volatility has affected the market prices of securities issued by many companies for reasons unrelated to their operating performance and may adversely affect the price of our Common Stock. In addition, our announcements of our quarterly operating results, changes in general conditions in the economy or the financial markets and other developments affecting us, our Affiliates or our competitors could cause the market price of our Common Stock to fluctuate substantially.

        In addition, the sale of substantial amounts of our Common Stock could adversely impact its price. We may issue additional shares of our Common Stock in connection with our financing activities, as described previously. Furthermore, as of December 31, 2002, options to purchase 4,267,007 shares of our Common Stock were outstanding (of which 2,215,869 were exercisable). In the event that a large number of shares of our Common Stock are sold in the public market, the price of our Common Stock may fall.

Our Web Site

        Our web site is located at http://www.amg.com. Our web site provides information on us and our Affiliates, as well as a link in the "Investor Information" section of our web site to another web site where you can obtain, free of charge, a copy of our Annual Reports on Form 10-K, Quarterly Reports

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on Form 10-Q, Current Reports on Form 8-K and any amendments to those reports filed with the Securities and Exchange Commission pursuant to the Exchange Act, following our filing of such material with the Securities and Exchange Commission.

Item 2. Properties

        Our executive offices are located at 600 Hale Street, Prides Crossing, Massachusetts 01965. We have entered into an operating lease for these offices that expires in December 2006. The lease includes renewal options that can be exercised at the end of the lease term, and purchase options that can be exercised prior to the expiration of the lease term. We believe that the property is suitable for our use for the foreseeable future.

        Each of our Affiliates leases office space in the city or cities in which it conducts business.

Item 3. Legal Proceedings

        From time to time, we and our Affiliates may be parties to various claims, suits and complaints. Currently, there are no such claims, suits or complaints that, in our opinion, would have a material adverse effect on our financial position, liquidity or results of operations.

Item 4. Submission of Matters to a Vote of Security Holders

        No matters were submitted to a vote of stockholders during the fourth quarter of the year covered by this Annual Report on Form 10-K.

PART II

Item 5. Market for Registrant's Common Equity and Related Stockholder Matters

        Our Common Stock is traded on the New York Stock Exchange (symbol: AMG). The following table sets forth the high and low closing prices as reported on the New York Stock Exchange composite tape since January 1, 2001.

(1)

Data for this period reflects high and low closing prices from January 1, 2003 through March 25, 2003.

        The closing price for a share of our Common Stock on the New York Stock Exchange on March 25, 2003 was $43.04.

        As of December 31, 2002 and March 25, 2003, there were 44 stockholders of record.

        We have not declared a dividend with respect to the periods presented. Since we intend to retain earnings to finance investments in new Affiliates, repay indebtedness, pay interest and income taxes, repurchase shares of our Common Stock when appropriate and develop our existing business, and since our credit facility prohibits us from making dividend payments to our stockholders, we do not anticipate paying dividends on our Common Stock in the foreseeable future.

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Item 6. Selected Historical Financial Data

        Set forth below are selected financial data for the last five years. This data should be read in conjunction with, and is qualified in its entirety by reference to, the financial statements and accompanying notes included elsewhere in this Form 10-K.