Hewitt Associates, Inc. to Merge with Aon Corporation

Transaction Creates Global Leader in Human Capital Solutions

CHICAGO, Illinois, July 12, 2010 - Aon Corporation (NYSE: AON) and Hewitt Associates, Inc. (NYSE: HEW)
announced today that the boards of directors of both companies have approved
a definitive agreement under which Hewitt will merge with a subsidiary of
Aon. The aggregate consideration is valued at $50 per Hewitt share, which
represents a 41% premium to Hewitt's closing stock price on July 9, 2010, the
last trading day prior to the announcement of the agreement. The aggregate
fully diluted equity value of the transaction is approximately $4.9 billion,
consisting of 50% cash and 50% Aon stock (based on the closing price of Aon
common stock on July 9, 2010).

Following the close of the transaction, Aon intends to integrate Hewitt
with its existing consulting and outsourcing operations (Aon Consulting) and
operate the segment globally under the newly created Aon Hewitt brand. In
addition, Russ Fradin, chairman and chief executive officer of Hewitt, will
serve as chairman and chief executive officer of Aon Hewitt, reporting to
Greg Case, chief executive officer, Aon Corporation.

Hewitt is one of the world's leading HR consulting and outsourcing
companies. Hewitt helps more than 3,000 clients and their employees around
the world anticipate and solve their most complex benefits, talent, and
related financial challenges through three primary business lines:
consulting, benefits outsourcing and HR business process outsourcing. Hewitt,
combined with Aon Consulting, will build upon those strengths, creating a
global leader in human capital solutions, with diverse product and service
capabilities and world-class associates to effectively serve clients'
evolving needs.

"This agreement reflects our ongoing efforts to ensure that Aon's
associates, capabilities and technology remain at the forefront of our
industry, providing distinctive client value," said Case. "As we continue to
grow our business, this merger will give us a broader portfolio of innovative
products and services focused on what we believe are two of the most
important topics in the global economy today - risk and people."

Case continued, "Aon and Hewitt share a focus on excellence in client
service and recognize the importance of talent in our industry. A leading
portfolio of client services and strong cultural fit will enable us to
quickly realize the benefits of this transaction, and the value added for our
clients, our associates and our stockholders."

"We are extremely excited to join forces with another iconic global brand
to form the leading human capital services enterprise," commented Fradin.
"This combination allows us to provide even more services for our clients and
greater opportunities for our associates. Aon and Hewitt share a relentless
commitment to our clients and to the associates who serve them."

An integration team led by Greg Besio (chief administrative officer, Aon)
will commence planning for a strong transition. The team is comprised of
leaders across Aon and Hewitt and includes: Kristi Savacool (senior vice
president, Hewitt Large Markets Benefits Outsourcing), Jim Konieczny
(president, Hewitt HR Business Process Outsourcing), Yvan Legris (president,
Hewitt Consulting) and Kathryn Hayley (co-chief executive officer, Aon
Consulting).

Strategic Rationale of the Transaction

Aon believes the combination of Aon and Hewitt creates a global leader in
human capital solutions, benefitting clients, associates and stockholders in
several ways, including:

    - Aon Hewitt revenues of $4.3 billion and 29,000 associates globally.
    Combined revenues for fiscal year 2009 consist of 49% from consulting
    services, 40% from benefits outsourcing and 11% from HR business process
    outsourcing, creating more resources for associates and more
    opportunities to distinctively serve clients with capabilities in greater
    than 120 countries around the world;

    - Leading global brand and client service recognition worldwide. Premier
    Hewitt brand will be leveraged along with Aon's client recognition for
    leading employee benefits consulting firm;

    - Complementary product and service portfolio across consulting, benefits
    outsourcing and HR business process outsourcing. Product portfolio will
    provide for significant cross-sell opportunities including the marketing
    of Hewitt's benefits outsourcing and HR business process outsourcing
    services to Aon's clients, as well as the marketing of Aon's industry-
    leading risk services product portfolio to Hewitt's clients;

    - Diversified presence across large corporate and middle market. The
    combined client base will provide significant cross-sell opportunities to
    leverage Hewitt's predominantly large corporate client base with Aon's
    predominantly middle market client base;

    - Cost savings and operational efficiencies. The transaction is expected
    to generate approximately $355 million in annual cost savings across Aon
    Hewitt in 2013, primarily from reduction in back-office areas, public
    company costs, management overlap and leverage of technology platforms;

    - Expect to achieve an operating margin in Aon Hewitt of 20%. Primarily
    through anticipated synergies and greater economies of scale, Aon Hewitt
    expects to deliver improved operational performance and a long-term
    operating margin of 20%;

    - Expect to create $1.5 billion of value creation. Strong cash flow
    generation of Hewitt, combined with anticipated synergies from the
    combination, are expected to deliver $1.5 billion of value creation for
    stockholders on a discounted cash flow basis, after subtracting the
    purchase price of the transaction.

            Estimated EPS Accretion / Dilution

                           2011          2012         2013
    EPS - GAAP            -8.4%          1.2%         5.8%
    EPS - Adjusted (1)     1.2%          5.4%         5.8%

    (1) Excludes one-time restructuring costs of $249 million ($168
    million in 2011 and $81 million in 2012)

Aon expects the transaction to be accretive on a GAAP EPS basis in 2012
and on an Adjusted EPS basis in 2011. Aon expects the transaction to be
significantly accretive to cash earnings in 2011. On a risk adjusted basis,
the transaction is expected to deliver an improvement of approximately 100
bps to return on invested capital (ROIC) when compared to potential share
repurchase over the time-frame of the transaction.

Transaction Summary

Hewitt will merge with a subsidiary of Aon. Hewitt stockholders will be
entitled to receive for each share of Hewitt common stock, $25.61 in cash and
0.6362 of a share of Aon common stock. Based on the closing price of Aon
common stock on July 9, 2010, the aggregate consideration paid on a fully
diluted basis is valued at $50 per Hewitt share. The consideration represents
a 41% premium to Hewitt's closing stock price on July 9, 2010, the last
trading day prior to the announcement of the agreement. The definitive
agreement also contains an election procedure allowing each Hewitt
stockholder to seek all cash or all stock, subject to proration and
adjustment.

The aggregate fully diluted equity value of the transaction is
approximately $4.9 billion, consisting of $2.45 billion of cash and the
issuance of 64.0 million shares, including the rollover of certain Hewitt
options into options to purchase Aon stock. The consideration reflects a
multiple of approximately 7.5 times Hewitt's fiscal year 2010 consensus
estimates EBITDA.

Financing commitments from Credit Suisse and Morgan Stanley for 100% of
the cash consideration are in place for a three-year $1.0 billion bank term
loan and a $1.5 billion bridge loan facility. Aon expects to issue unsecured
notes prior to drawing on the bridge loan facility.

The transaction is expected to close by mid-November, subject to
customary closing conditions, regulatory approvals, as well as approval by
both Aon and Hewitt stockholders.

Advisors

Credit Suisse acted as financial advisor to Aon, and Sidley Austin LLP is
serving as legal counsel. Citigroup Global Markets Inc. served as exclusive
financial advisor to Hewitt, and Debevoise & Plimpton LLP and Paul, Weiss,
Rifkind, Wharton & Garrison LLP are serving as legal counsel.

Analyst and Investor Conference Call and Webcast Details

Aon and Hewitt will host a conference call today, Monday, July 12, 2010
at 7:30 a.m. central time. Interested parties can listen to the conference
call by dialing (800) 369-3129 (within the U.S.), (312) 470-7363 (outside of
the U.S.) using access code: Aon, or via a live audio webcast at
www.aon.com and www.hewitt.com. Presentation slides that
provide an overview of the transaction will be available at both
www.aon.com and www.hewitt.com prior to the start of the
conference call.

A replay of the conference call will be available for 30 days following
the live conference call, and can be accessed by dialing (866)-417-5769
(within the U.S.) or (203)-369-0737 (outside of the U.S.), using access code:
4913. The replay will also be available at www.aon.com and
www.hewitt.com.

For more information:

www.hewitt.com.

www.aon.com .

Safe Harbor Statement

This communication contains certain statements related to future results,
or states our intentions, beliefs and expectations or predictions for the
future which are forward-looking statements as that term is defined in the
Private Securities Litigation Reform Act of 1995. These forward-looking
statements are subject to certain risks and uncertainties that could cause
actual results to differ materially from either historical or anticipated
results depending on a variety of factors. Potential factors that could
impact results include: the possibility that the expected efficiencies and
cost savings from the proposed transaction will not be realized, or will not
be realized within the expected time period; the ability to obtain
governmental approvals of the merger on the proposed terms and schedule
contemplated by the parties; the failure of stockholders of Hewitt to approve
the proposed merger; the failure of the stockholders if Aon to approve the
issuance of Aon common stock to Hewitt stockholders; the risk that the Aon
and Hewitt businesses will not be integrated successfully; disruption from
the proposed transaction making it more difficult to maintain business and
operational relationships; the possibility that the proposed transaction does
not close, including, but not limited to, due to the failure to satisfy the
closing conditions; general economic conditions in different countries in
which Aon and Hewitt do business around the world; changes in global equity
and fixed income markets that could affect the return on invested assets;
fluctuations in exchange and interest rates that could influence revenue and
expense; rating agency actions that could affect Aon's ability to borrow
funds; funding of Aon's various pension plans; changes in the competitive
environment; changes in commercial property and casualty markets and
commercial premium rates that could impact revenues; the outcome of inquiries
from regulators and investigations related to compliance with the U.S.
Foreign Corrupt Practices Act and non-U.S. anti-corruption laws; the impact
of investigations brought by U.S. state attorneys general, U.S. state
insurance regulators, U.S. federal prosecutors, U.S. federal regulators, and
regulatory authorities in the U.K. and other countries; the impact of class
actions and individual lawsuits including client class actions, securities
class actions, derivative actions and ERISA class actions; the cost of
resolution of other contingent liabilities and loss contingencies; and the
ability to realize the anticipated benefits to Aon of the Benfield merger.
Further information concerning Aon, Hewitt, and their business, including
factors that potentially could materially affect Aon's and Hewitt's financial
results, is contained in Aon's and Hewitt's filings with the Securities and
Exchange Commission (the "SEC"). See Aon's and Hewitt's Annual Reports on
Form 10-K and Annual Reports to Stockholders for the fiscal years ended
December 31, 2009 and 5 September 30, 2009, respectively, and other public
filings with the SEC for a further discussion of these and other risks and
uncertainties applicable to our businesses. Neither Aon nor Hewitt
undertakes, and each of them expressly disclaims, any duty to update any
forward-looking statement whether as a result of new information, future
events or changes in their respective expectations, except as required by
law.

Additional Information

This communication does not constitute an offer to sell or the
solicitation of an offer to buy our securities or the solicitation of any
vote or approval. This communication is being made in respect of the proposed
transaction involving Aon and Hewitt. In connection with the proposed
transaction, Aon and Hewitt will be filing documents with the SEC, including
the filing by Aon of a registration statement on Form S-4, and Aon and Hewitt
intend to mail a joint proxy statement regarding the proposed merger to their
respective stockholders that will also constitute a prospectus of Aon. Before
making any voting or investment decision, investors and stockholders are
urged to read carefully in their entirety the joint proxy
statement/prospectus regarding the proposed transaction and any other
relevant documents filed by either Aon or Hewitt with the SEC when they
become available because they will contain important information about the
proposed transaction. You may obtain copies of all documents filed with the
SEC regarding this transaction, free of charge, at the SEC's website
(www.sec.gov), by accessing Aon's website at www.aon.com under the heading
"Investor Relations" and then under the link "SEC Filings" and from Aon by
directing a request to Aon at Aon Corporation, 200 E. Randolph Street,
Chicago, Illinois 60601, Attention: Investor Relations, and by accessing
Hewitt's website at www.hewitt.com under the heading "Investor Relations" and
then under the link "Reports & SEC Filings" and from Hewitt by directing a
request to Hewitt at Hewitt Associates, Inc., 100 Half Day Road,
Lincolnshire, Illinois 60069, Attention: Investor Relations.

Aon and Hewitt and their respective directors and executive officers and
certain other members of management and employees may be deemed to be
participants in the solicitation of proxies in respect of the proposed
transaction. You can find information about Aon's directors and executive
officers in its definitive proxy statement filed with the SEC on April 7,
2010. You can find information about Hewitt's directors and executive
officers in its definitive proxy statement filed with the SEC on December 16,
2009. Other information regarding the participants in the proxy solicitation
and a description of their direct and indirect interests, by security
holdings or otherwise, will be contained in the joint proxy
statement/prospectus and other relevant materials to be filed with the SEC
when they become available. You can obtain free copies of these documents
from Aon and Hewitt using the contact information above.

Investor Contact: Scott Malchow, Aon Corporation, Vice President, Investor Relations, +1-312-381-3983; Investor Contact: Sean McHugh, Hewitt Associates, Vice President, Investor Relations, +1-847-442-4176; Media Contact: David Prosperi, Aon Corporation, Vice President, Global Public Relations, +1-312-381-2485; Media Contact: Maurissa Kanter, Hewitt Associates, Director, Public Relations, +1-847-442-0952