Exhibit 99.1

Marsh & McLennan Companies, Inc.

JLT Supplemental Information – Revenue Analysis

For the Year Ended December 31, 2018

(Millions) (Unaudited)

JLT revenue is presented below, and reflects certain transfers among the business lines to conform with the expected inclusion in MMC segment and business results.

	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Full Year
Specialty	$	244	$	352	$	259	$	406	$	1,261
Reinsurance	124		74		33		48		279
Fiduciary Interest Income	3		4		5		5		17
Health & Benefits	86		86		86		99		357
Total Revenue	$	457	$	516	$	383	$	558	$	1,914

In future earnings releases Specialty will be included as a component of Marsh, Reinsurance as a component of Guy Carpenter and Health & Benefits as a component of Mercer.

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Marsh & McLennan Companies, Inc.

JLT Supplemental Information–Adjusted Operating Income Information*

For the Year Ended December 31, 2018

(Millions) (Unaudited)

	First Quarter		Second Quarter		Third Quarter			Fourth Quarter		Full Year
Revenue	$	457	$	516	$	383		$	558	$	1,914
Expense:
Compensation and Benefits	314		318		300			278		1,210
Other Operating Expenses	117		115		103			146		481
Operating Expenses	431		433		403			424		1,691
Operating Income	$	26	$	83	$	(20	)	$	134	$	223
Noteworthy Items:
Restructuring	12		12		6			7		37
Regulatory Review	—		2		—			47		49
Other	—		—		—			4		4
Total Adjustments	$	12	$	14	$	6		$	58	$	90
Supplemental Adjusted Operating Income	$	38	$	97	$	(14	)	$	192	$	313

*See Note 1 for discussion of Non-GAAP measures.

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Marsh & McLennan Companies, Inc.

Supplemental Information– Basis for Presentation– Non-GAAP Information

Note 1: Financial information included herein reflects the following:

The unaudited financial information presented herein is derived from the column "Conformed JLT (U.S. GAAP)” included on page 2 of the Company’s Form 8-K/A filed on June 6, 2019. This information includes the reclassifications and adjustments to JLT’s historical IFRS income statement described in Notes 3 and 5 of that 8-K/A filing. The operating income of $223 million includes the results of JLT’s aerospace business and excludes the incremental amortization of intangibles related to the JLT acquisition.

Non-GAAP Measures:

The Company reports its financial results in accordance with accounting principles generally accepted in the United States (referred to as "GAAP" or "As Reported" results). The Company also refers to and presents certain additional non-GAAP financial measures, within the meaning of Regulation G under the Securities Exchange Act of 1934. All information included herein is non-GAAP.

The Company believes these non-GAAP financial measures provide useful supplemental information that enables investors to better compare the Company’s performance across periods. Management also uses these measures internally to assess the operating performance of its businesses, to assess performance for employee compensation purposes and to decide how to allocate resources. However, investors should not consider these non-GAAP measures in isolation from, or as a substitute for, the financial information that the Company reports in accordance with GAAP. The Company’s non-GAAP measures include adjustments that reflect how management views our businesses, and may differ from similarly titled non-GAAP measures presented by other companies.

Supplemental Adjusted Operating Income (Loss)

Adjusted operating income (loss) is calculated by excluding the impact of certain noteworthy items from the Company’s GAAP operating income or loss. The tables in the Company’s quarterly earnings releases identify these noteworthy items and reconcile adjusted operating income (loss) to GAAP operating income or loss, on a consolidated and segment basis. The non-GAAP adjustments reflected in the attached supplemental financial information are intended to provide investors with similar information related to JLT’s 2018 results. The noteworthy items related to JLT are included in the Adjusted Operating Income Information schedule.

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