EX-99.1

2018 ANNUAL

STOCKHOLDERS MEETING

May 15, 2018

Exhibit 99.1

18CORP23863J

Stockholders’ Meeting

May 15, 2018

•

2018 Annual Meeting

•

Chairman’s Remarks

•

2017 Review

•

Closing Comments

•

Questions & Answers

18CORP23863J

Stockholders’ Meeting

May 15, 2018

Please turn off all cell phones.

All audio and video recording

is prohibited.

18CORP23863J

2018 Board of Directors

•

Sherry S. Barrat

•

William L. Bax

•

D. John Coldman

•

Frank E. English, Jr.

•

Elbert O. Hand

•

David S. Johnson

•

Kay W. McCurdy

•

Ralph J. Nicoletti

•

Norman L. Rosenthal, Ph.D.

18CORP23863J

Stockholders’ Meeting

May 15, 2018

•

2018 Annual Meeting

18CORP23863J

Stockholders’ Meeting

May 15, 2018

•

2018 Annual Meeting

•

Chairman’s Remarks

•

2017 Review

18CORP23863J

Cautionary Note on New Accounting Standard

and Information on Forward-Looking Statements

Cautionary Note Regarding New Revenue Recognition Accounting Standard

The

financial

information

the

slides

that

are

presented

under

“Old

GAAP”

–

i.e.,

before

implementation

the

new

revenue

recognition

accounting

standard

(ASC

Topic 606), which we adopted as of January 1, 2018, using the full retrospective method. Accordingly, the financial information for 2017 presented in these slides may not

be identical to the financial information for 2017 presented in our filings with the SEC beginning with our Quarterly Report on Form 10-Q for the quarter ended March 31,

2018.

Information Regarding Forward-Looking Statements

This presentation contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Examples of forward-looking statements

in this presentation include, but are not limited to, statements regarding: (i) our ability to leverage resources across borders; (ii) future dividends; (iii) improvements in our

new business production; (iv) “tuck-in” M&A activity; (v) global brand recognition; (vi) the leveraging of internal resources across divisions and borders; (vii) our status as the

premier provider of claims management services; (viii) our global presence in the claims space; (ix) our ability to stay in front of improvements in technology; (x) commercial

P&C pricing; (xi) drivers and expected levels of our organic growth; (xii) future M&A opportunities, including bolt-on acquisitions to our “platforms”; (xiii) increasing

productivity

and

quality;

(xiv)

our

management

team;

(xv)

our

use

leverage;

(xvi)

our

balance

sheet;

and

(xvii)

our

return

shareholders.

Important factors that could cause actual results to differ materially from those in the forward-looking statements include: declines in premiums or other adverse trends in the

insurance industry; an economic downturn (including as a result of Brexit); tax reform, including new interpretations or guidance from regulators; competitive pressures in

our businesses; failure to successfully or cost-effectively integrate recently acquired businesses; risks to our acquisition strategy, including continuing consolidation in our

industry

and

increased

interest

acquiring

insurance

brokers

private

equity

firms;

our

failure

attract

and

retain

key

executives

and

other

personnel;

risks

arising

from

our international operations, including political and economic uncertainty and regulatory and legal compliance risk; concentration of large amounts of revenue with certain

clients in our risk management segment; failure to apply technology effectively in our businesses; business continuity and cybersecurity risks; damage to our reputation; and

failure to comply with regulatory requirements, including the FCPA, other anti-corruption laws, and data privacy laws.

Please

refer

Gallagher’s

filings

with

the

SEC,

including

Item

1A,

“Risk

Factors,”

its

most

recently

filed

Annual

Report

Form

10-K

and

Quarterly

Report

Form

10-Q

for a more detailed discussion of these and other factors that could impact its forward-looking statements.

18CORP23863J

This presentation includes references to Adjusted EBITDAC, Adjusted EBITDAC margin, Adjusted Revenues, Adjusted Operating Expense Ratio and Organic Revenue Growth, which are measures not in accordance with, or an alternative to, the GAAP

information provided herein.

Earnings

Measures

Gallagher

believes

that

each

Adjusted

EBITDAC

and

Adjusted

EBITDAC

margin,

defined

below,

provides

meaningful

representation

its

operating

performance

and

improves

the

comparability

Gallagher’s

results

between

periods by eliminating the impact of certain items that have a high degree of variability.

EBITDAC is defined as net earnings before interest, income taxes, depreciation, amortization and the change in estimated acquisition earnout payables.

Adjusted

EBITDAC

further

adjusted

exclude

gains

realized

from

sales

books

business,

acquisition

integration

costs

large

acquisitions,

workforce

charges,

lease

termination

charges,

acquisition

related adjustments and the period-over-period impact of foreign currency translation, as applicable.

Adjusted

EBITDAC

margin

defined

Adjusted

EBITDAC

divided

Adjusted

Revenues

(defined

below).

The most directly comparable GAAP measure for these non-GAAP earnings measures is net earnings. For the two segments (Brokerage Segment & Risk Management Segment) on a combined basis, net earnings was $174 million, $199 million, $253 million,

$306 million, $325 million, $414 million and $484 million in 2011, 2012 , 2013, 2014, 2015, 2016 and 2017. For the Brokerage Segment, net earnings were $357 million and $424 million in 2016 and 2017, respectively. For the Risk Management Segment, net

earnings were $57 million and $60 million in 2016 and 2017, respectively. See Cautionary Note on page 7.

Revenue

and

Expense

Measures

Gallagher

believes

that

Adjusted

Revenues

and

Adjusted

Operating

Expense Ratio, each as defined below, provides stockholders and other interested persons with useful information that will assist such persons in

analyzing Gallagher’s operating results as they develop a future outlook for Gallagher. Gallagher believes that Organic Revenue Growth provides a comparable measurement of revenue growth that is associated with the revenue sources that will continue in

the future.

Gallagher has historically viewed organic revenue growth as an important indicator when assessing and evaluating the performance of its Brokerage and Risk Management segments. Gallagher also believes that using this measure allows financial

statement users to measure, analyze and compare the growth from its Brokerage and Risk Management segments in a meaningful and consistent manner.

Adjusted

Revenues

defined

revenues,

adjusted

exclude

gains

realized

from

sales

books

business,

acquisition

integration

costs

for

large

acquisitions,

workforce

charges,

lease

termination

charges,

acquisition

adjustments, and the period-over-period impact of foreign currency translation, as applicable.

Adjusted Operating Expense Ratio

is defined as operating expense, adjusted to exclude the items listed above for Adjusted Revenues, as applicable, divided by Adjusted Revenues.

Organic

Revenue

Growth.

For

the

Brokerage

segment,

organic

change

commission

and

fee

revenues

excludes

the

first

twelve

months

net

commission

and

fee

revenues

generated

from

acquisitions

and

the

net

commission

and

fee

revenues

operations

disposed

each

year

presented.

These

commissions

and

fees

are

excluded

from

organic

revenues

order

help

interested

persons

analyze

the

revenue growth associated with the operations that were a

part

Gallagher

both

the

current

and

prior

year.

addition,

change

commission

and

fee

revenue

organic

growth

excludes

the

period-over-period

impact

foreign

currency

translation. For the Risk Management segment, organic change in

fee

revenues

excludes

the

first

twelve

months

fee

revenues

generated

from

acquisitions

and

the

fee

revenues

operations

disposed

each

year

presented.

addition, change in organic growth excludes the impact of the period-

over-period impact of foreign currency translation to improve the comparability of our results between periods by eliminating the impact of the items that have a high degree of variability or are due to the limited-time nature of these revenue

sources.

The most directly comparable GAAP measure for Adjusted Revenues and Organic Growth is reported revenues. For the Brokerage Segment, reported revenues were $533 million, $679 million, $783 million, $863 million, $946 million, $1,007 million, $1,114

million, $1,188 million, $1,276 million, $1,329 million, $1,544 million, $1,812 million, $2,126 million, $2,896 million, $3,324 million, $3,528 million and $3,831 million in 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011,

2012, 2013, 2014, 2015 , 2016 and 2017, respectively. For the Risk Management Segment, reported revenues were $718 million and $769 million in 2016 and 2017, respectively. On a combined basis (Brokerage Segment & Risk Management

Segment)

reported

revenues

were

$4,246

million

and

$4,599

million

2016

and

2017,

respectively.

See

Cautionary

Note

page 7.

The most directly comparable GAAP measure for Adjusted Operating Expense Ratio is reported operating expense, which was $247 million and $614 million in 2008 and 2017, respectively, for the Brokerage Segment

and $126 million and $189 million in 2008 and 2017, respectively, for the Risk Management Segment.

Revenue

Recognition

Accounting

Guidance.

These

slides

present

financial

information

for

periods

prior

our

adoption

the

new

revenue

recognition

accounting

guidance,

ASC

Topic

606.

All

such

pre-adoption

financial

information

non-GAAP.

Gallagher’s management believes this non-GAAP information is useful to investors because it assists them in understanding our year-over-year financial performance for periods prior to adoption of the new accounting standard. The 2017 information is

provided

for

illustrative

purposes

only,

and

should

read

together

with,

and

not

considered

substitute

for,

the

Company’s

historical

financial

statements.

The

financial

information

for

2017

does

not

constitute

restatement of the Company’s historical

financial statements previously filed with the Securities and Exchange Commission.

Reconciliations

–

For

reconciliations,

please

see

the

examples

set

forth

our

filings

with

the

Securities

and

Exchange

Commission

covering

periods

prior

our

adoption

the

new

revenue

recognition

accounting standard.

Information Regarding

Non-GAAP Measures

18CORP23863J

52-Week Range***

70.55 Hi

53.63 Lo

2.5%

Dividend

Yield***

0.41

•

Founded in 1927

•

Public since 1984

•

One of the World’s leading insurance brokers*

•

One of the World’s largest P&C third-party administrators*

As of December 31, 2017 unless otherwise indicated

Acquired

Revenues 2017**

172M

4.6B

2017 Total

Adjusted Revenue**

Countries***

11.8B

AJG

Who We Are

Key Facts

Key Shareholder Data

* According to Business Insurance

** Brokerage & Risk Management adjusted revenue

*** as of February 6, 2018

2018 Q1

Dividend/Share

Market

Cap***

NYSE

Employees

26,783

Outstanding

181.0M

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*Brokerage and Risk Management adjusted revenue for the year ended December 31, 2017.

Snapshot of Core Operations

RISK

MANAGEMENT

SEGMENT

BROKERAGE

SEGMENT

•

83% of revenue*

•

We sell insurance and consult on insurance programs

•

Property/Casualty and employee benefits

•

Retail and wholesale

•

Primarily middle-market commercial clients and individuals

•

77%

C&F

revenue

commission

–

23%

fee-based

•

17% of revenue*

•

We adjust claims and help companies and carriers reduce their losses

•

Workers’ compensation, liability, managed care, auto and property

•

Modest amount of storm/earthquake claims

•

Primarily Fortune 1000 clients

•

More than 90% of revenue* from non-affiliated brokerage customers and

their clients

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Risk Management*

Brokerage*

Diverse Revenue Base

*Brokerage and Risk Management adjusted revenue for the year ended December 31, 2017.

57%

26%

17%

WHOLESALE

RETAIL P/C

RETAIL BENEFITS

66%

34%

DOMESTIC

INTERNATIONAL

87%

13%

DOMESTIC

INTERNATIONAL

64%

LIABILITY

32%

PROPERTY

WORKERS’

COMPENSATION

18CORP23863J

(in $M)

Brokerage Segment

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard. See also important

disclosures regarding Non-GAAP measures on Page 8.

$3,508

$3,827

$3,400

$3,600

$3,800

$4,000

2016

2017

Adjusted Revenues

(in $M)

3.6%

4.4%

2.0%

3.0%

4.0%

5.0%

2016

2017

Total Organic Growth

26.9%

27.4%

26.0%

27.0%

28.0%

2016

2017

Adjusted EBITDAC Margin

$945

$1,050

$900

$1,000

$1,100

2016

2017

Adjusted EBITDAC

11%

18CORP23863J

(in $M)

Risk Management Segment

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard. See also important

disclosures regarding Non-GAAP measures on Page 8.

$720

$769

$700

$720

$740

$760

$780

2016

2017

Adjusted Revenues

(in $M)

1.3%

5.2%

0.0%

2.0%

4.0%

6.0%

2016

2017

Total Organic Growth

$125

$133

$120

$125

$130

$135

$140

2016

2017

Adjusted EBITDAC

17.4%

15.0%

16.0%

17.0%

18.0%

2016

2017

Adjusted EBITDAC Margin

18CORP23863J

(in $M)

Brokerage & Risk Management

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard. See also important

disclosures regarding Non-GAAP measures on Page 8.

$4,228

$4,596

$4,000

$4,250

$4,500

$4,750

2016

2017

Adjusted Revenues

(in $M)

3.1%

4.5%

1.0%

2.0%

3.0%

4.0%

5.0%

2016

2017

Total Organic Growth

$1,070

$1,183

$1,000

$1,050

$1,100

$1,150

$1,200

$1,250

2016

2017

Adjusted EBITDAC

11%

25.3%

25.8%

24.5%

25.0%

25.5%

26.0%

2016

2017

Adjusted EBITDAC Margin

18CORP23863J

(in $M)

Net Earnings from

Clean Energy Investments

*Excludes a non-cash after tax gain of $14.1m from a re-consolidation accounting gain, related to clean-energy

investments, recorded in 2014.

-$4.8

$7.5

$3.9

$32.7

$63.7

$90.5

$100.9

$114.4

$132.7

-$10

$10

$20

$30

$40

$50

$60

$70

$80

$90

$100

$110

$120

$130

$140

2009

2010

2011

2012

2013

2014*

2015

2016

2017

18CORP23863J

1984

2018E

$1.64*

Dividends Per Share

*Indicated –

On January 24, 2018, Gallagher’s Board of Directors declared a $0.41 per share first-quarter 2018 dividend.

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

$1.40

$1.60

$1.80

18CORP23863J

adjusted revenue growth

4.5%

total organic growth

11%

adjusted EBITDAC growth

46 bps

margin improvement

2017 Business Highlights

Brokerage & Risk Management Combined

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard. See also important

disclosures regarding Non-GAAP measures on Page 8.

18CORP23863J

$172.3m

in acquired revenues

+39

additional –

average $4.4m in revenue

~8.0x EBITDAC

Fair valuations

tuck-in opportunities

Focus on

2017 Business Highlights

Mergers & Acquisitions

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard. See also important

disclosures regarding Non-GAAP measures on Page 8.

18CORP23863J

$132.7m

of net earnings

16%

increase in net earnings over

2016

2017 Business Highlights

Clean Energy

18CORP23863J

Global M&A integration

Completed

Australia/New Zealand

& Canada

Completed

U.K. retail

2017 integration costs less than a third of 2016 costs

2017 Business Highlights

All while accomplishing…

18CORP23863J

Where We Are Going

BROKERAGE

SEGMENT

•

Improving new business production

•

Continuing tuck-in M&A

•

Increasing global brand recognition

•

Leveraging internal resources and processes across divisions

•

To be premier provider of claims management services with superior outcomes

•

Increasing global presence in claims space

•

U.S. clients with global operations

•

Expanding via M&A/new partners

•

Staying in front of improving technology

•

Increasing brand recognition globally

•

Leveraging resources across borders

RISK

MANAGEMENT

SEGMENT

18CORP23863J

Commercial P&C Pricing Shows

Shallow Cycle

Commercial Rate Index reflects the cost of P&C premiums relative to the year 2000. Constructed using Counsel of Insurance Agents

and Brokers (CIAB) data. CPI index uses data from the Bureau of Labor Statistics.

CPI

142

Rates

100

110

120

130

140

150

160

18CORP23863J

Shows Shallow Pricing Cycle

-2.9%

-0.1%

0.9%

2.7%

4.4%

4.3%

3.9%

5.0%

5.2%

4.3%

3.4%

2.1%

1.5%

-0.5%

0.1%

-0.7%

-2.3%

-3.3%

-3.1%

-2.8%

-3.7%

-3.9%

-3.2%

-3.3%

-2.5%

-2.8%

-1.3%

0.3%

-6.0%

-4.0%

-2.0%

0.0%

2.0%

4.0%

6.0%

CIAB –

Change in Average Commercial Rates

18CORP23863J

Hard Market

Shallow Market

CIAB

Sales Culture Performs Through Cycle

CIAB is the 4 quarter average. Gallagher’s Brokerage Segment Organic Growth excluding Contingent Commissions. See Cautionary Note on

page 7 regarding the new revenue recognition accounting standard. See also important disclosures regarding Non-GAAP measures on Page 8.

14.0%

16.0%

10.0%

2.0%

5.0%

2.0%

-0.8%

-2.4%

-1.7%

3.1%

4.4%

5.6%

3.8%

3.4%

4.4%

19.8%

8.1%

-4.1%

-8.0%

-5.2%

-12.1%

-11.0%

-5.4%

-5.6%

0.2%

4.4%

3.8%

0.1%

-2.9%

-3.5%

-1.6%

-15.0%

-10.0%

-5.0%

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

2001

2003

2005

2007

2009

2011

2013

2015

2017

Gallagher Brk Organic

CIAB -

Change in Avg. Commercial Rates

Soft Market

AJG Brk

Organic

18CORP23863J

CLIENTS

CARRIERS

& BROKERS

Shallow Rate Cycle Is Better for:

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Consistent Growth Strategy

18CORP23863J

Consistent Growth Strategy –

Organic

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Driving Brokerage Organic Growth

18CORP23863J

Aviation

Automotive

Affinity

Real Estate/

Hospitality

Global Risks

Construction

Personal

Marine

Higher Education

Healthcare

Environmental

Entertainment

Energy

Private Client

Public Entity

Religious

Restaurant

Technology

Trade Credit/

Political Risk

Transportation

Financial Institutions

K12 Education

Not-for-Profit

Equity Advisors

Food/Agribusiness

Life Sciences

Law Firms

Niche Expertise Teams –

Brokerage

18CORP23863J

Driving Risk Management

Organic Growth

18CORP23863J

ALTERNATIVE

MARKET

PARTICIPANTS

LARGE

COMMERCIAL

ENTITIES

PUBLIC

SECTOR

ENTITIES

INSURANCE

CARRIERS

Risk Management Growth

Focuses on Four Market Segments

18CORP23863J

Consistent

Growth

Strategy

–

M&A

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Acquisition Revenue Growth

Annualized Revenues Acquired (in $M’s)

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard.

$100

$200

$300

$400

$500

$600

$700

$800

$900

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

Domestic Property & Casualty

Employee Benefits

Risk Management

Foreign Property & Casualty

Vast Pipeline

Domestic and international

markets highly fragmented

18,000+ agents/ brokers just

in the U.S.

Need Gallagher’s expertise

Baby boomers looking for

exit strategy

Acquisition Units

Retail P&C

Wholesale

Benefits

International

MGA/MGU

Captive

TPA

Limited Consolidators

Core Competency

Culture

Proven history

Ability to integrate

M&A Opportunities Continue

18CORP23863J

Platforms In Place for Bolt-on M&A

18CORP23863J

Client Capabilities

in 150 Countries

International Correspondent

Broker Network

18CORP23863J

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Productivity and Quality Initiatives

18CORP23863J

Building

Productivity

Tools –

DMS

and Workflow

Optimizing Real

Estate Footprint

Investing in

Business

Intelligence

Leveraging

Sales Force

Management

Tools

CONTINUE TO

IMPROVE

PRODUCTIVITY

AND QUALITY

Utilizing

Centers of

Excellence

Harmonizing

Systems

Utilizing

Sourcing

to Manage

Expenses

Standardizing

Processes

Focus Continues:

Optimizing Productivity & Quality

18CORP23863J

Benefits Continue:

From Centers of Excellence

Foster

Innovation

Increase

Speed to Market

Reduce Costs

Focus on Core

Improve

Quality

Behind the Scenes Efforts

Centers of Excellence Update

We now have more than 3,500

associates in three locations

18CORP23863J

Policy

checking

Policy

issuance

Certificates of

insurance

Renewal

support

Accounting

support

Claims

support

Behind the Scenes Efforts

Centers of Excellence Update

Responsible for processes such as:

18CORP23863J

Substantially

improved

quality

Reduced both operating

and E&O costs

Easy for new

acquisition

partners to

leverage

Behind the Scenes Efforts

Centers of Excellence Update

18CORP23863J

18CORP23863J

Brokerage

Risk Management

Reduced Adjusted Operating

Expense Ratio

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard. See also important

disclosures regarding Non-GAAP measures on Page 8.

20.8%

15.6%

14.0%

15.0%

16.0%

17.0%

18.0%

19.0%

20.0%

21.0%

22.0%

2008

2017

27.0%

24.6%

23.0%

24.0%

25.0%

26.0%

27.0%

28.0%

2008

2017

18CORP23863J

Brokerage & Risk Management

Adjusted EBITDAC Margin

See Cautionary Note on page 7 regarding the new revenue recognition accounting standard. See also important

disclosures regarding Non-GAAP measures on Page 8.

20.4%

21.2%

22.1%

23.6%

24.5%

25.3%

25.8%

18.0%

19.0%

20.0%

21.0%

22.0%

23.0%

24.0%

25.0%

26.0%

27.0%

2011

2012

2013

2014

2015

2016

2017

Relentless

Focus on

Quality and

Customer

Service

Best

Companies

for

Leaders

–

2016

CHIEF EXECUTIVE MAGAZINE

Group

Risk

Adviser

the

Year

–

2017

UK CORPORATE ADVISER

Best

Employee

Benefit

Consultant

–

2016

REWARD GUIDE VIB AWARDS CEREMONY

Shilling

Named

Best

Member

Communication

Strategy

–

2016

UK CORPORATE ADVISER

Best

Sales/Leadership

Program

(non-store/restaurant)

–

2016

LEADERSHIP EXCELLENCE –

PART OF HR.COM

Insurance

Broker

the

Year

–

2017

2017 REACTIONS LONDON MARKET AWARDS

Caribbean

Broker

the

Year

–

2017

2017 REACTIONS LATIN AMERICA AWARDS

Top

“Best

Culture”

Company

Metro

Chicago

–

2017

USA TODAY

Best

Casualty

Claims

Handling

Insured/TPA

–

2017

ADVISEN CLAIMS SATISFACTION SURVEY

18CORP23863J

18CORP23863J

Maintaining Culture

The

Gallagher

Way

since 1927

Maintain Unique Culture

18CORP23863J

18CORP23863J

One of the World’s

Most Ethical Companies

as Recognized by Ethisphere

seven years in a row

•

Industry-leading commitment to

ethics and dedication to integrity

•

Chosen for:

Promoting ethical business

standards and practices

Exceeding legal compliance

standards

Innovating to benefit the public

Demonstrating that corporate

citizenship is tied to company

success

Why Invest?

•

Right management

•

Unique culture

•

Proven growth strategy

•

Continuing M&A opportunities

•

Increasing productivity/quality

•

Good use of leverage

•

Strong balance sheet

•

Excellent return to shareholders

You Believe Our

Company Has:

GALLAGHER IS

WELL-POSITIONED

FOR FUTURE

GROWTH

18CORP23863J

S&P

500

158

641

AJG

Why Invest? We Are Just

Getting Started!

Source

for

data:

Bloomberg.

Total

returns

from

1/1/2000

–

12/31/2017

include

reinvestment

dividends.

18CORP23863J

18CORP23863J

Additional Information:

Ray Iardella

Vice President, Investor Relations

Ray_Iardella@ajg.com

Phone: 630 285-3661