Exhibit 99.1

ALLIED WORLD REPORTS 53% GROWTH IN UNDERWRITING INCOME

FOR THE THIRD QUARTER 2013

• Diluted book value per share of $99.16, an increase of 3.1% from June 30, 2013

• Combined ratio of 84.2%, compared with 88.1% a year ago

• Gross premiums written increased 15.2% compared to the third quarter 2012

• Net favorable reserve development on prior loss years of $61.5 million versus $56.2 million a year ago

• The company repurchased $40.6 million of its common shares during the third quarter 2013

ZUG, Switzerland--(BUSINESS WIRE)-- Allied World Assurance Company Holdings, AG (NYSE: AWH) today reported net income of $122.8 million, or $3.54 per diluted share, for the third quarter of 2013 compared to net income of $219.6 million, or $6.00 per diluted share, for the third quarter of 2012. Net income for the nine months ended September 30, 2013 was $280.0 million, or $7.97 per diluted share, compared to net income of $534.2 million, or $14.28 per diluted share, for the first nine months of 2012.

The company reported operating income of $101.8 million, or $2.93 per diluted share, for the third quarter of 2013, compared to operating income of $79.2 million, or $2.16 per diluted share, for the third quarter of 2012. Operating income for the nine months ended September 30, 2013 was $289.5 million, or $8.24 per diluted share, compared to operating income of $258.0 million, or $6.90 per diluted share, for the first nine months of 2012.

President and Chief Executive Officer Scott Carmilani commented, “Once again, Allied World delivered an excellent underwriting performance. We benefitted from profitable growth across our well balanced, niche book of business amid an attractive rate environment. The improved investment environment also contributed to diluted book value per share growth of over 3% for the quarter.”

Third Quarter Summary (in thousands, except per share amounts) (Unaudited)

	Three months ended September 30,		Diluted per share
	2013	2012	2013	2012
Net income	$                    122,843	$          219,647	$                3.54	$                    6.00
Add after tax effect of:
Net realized investment gains	(25,395)	(141,451)	(0.73)	(3.86)
Foreign exchange loss	4,353	1,023	0.12	0.02
Operating income	$                    101,801	$            79,219	$                2.93	$                    2.16

Third Quarter Operating Results

• Gross premiums written were $580.9 million, a 15.2% increase compared to $504.4 million in the third quarter of 2012. This was attributable to growth across all three segments. U.S. Insurance grew by 17.3% helped by new business across existing lines including general casualty and programs, contributions from newer lines including primary construction, and premium rate increases across all lines of business; International grew by 9.5% in part due to new aviation business and from growth in professional liability lines across the European and Bermuda platforms; Reinsurance grew by 16.1% driven by new business in the specialty line.

• Net premiums written were $453.1 million, a 15.7% increase compared to $391.5 million in the third quarter of 2012.

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• Net premiums earned were $510.8 million, a 15.8% increase compared to $441.0 million in the third quarter of 2012.

• Underwriting income was $80.1 million, a 52.9% increase compared to $52.4 million in the third quarter of 2012 due to higher premiums earned as well as a fewer losses.

• The combined ratio was 84.2% compared to 88.1% in the third quarter of 2012 primarily due to a lower reported loss ratio offset by a slightly higher expense ratio.

• The loss and loss expense ratio was 54.2% in the third quarter of 2013 compared to 58.7% in the prior year. During the third quarter of 2013, the company recorded net favorable reserve development on prior loss years of $61.5 million, a benefit of 12.0 percentage points to the loss and loss expense ratio, compared to $56.2 million a year ago, a benefit of 12.7 percentage points.

• Excluding prior year reserve adjustments, the loss and loss expense ratio for the third quarter of 2013 was 66.2% compared to 71.4% for the third quarter of 2012.

• The company experienced no catastrophe losses for the quarter ended September 30, 2013.

• The company’s expense ratio was 30.0% for the third quarter of 2013 compared to 29.4% for the third quarter of 2012. The increase was largely driven by higher accruals for performance based compensation, the impact of a higher share price in the quarter on the stock compensation accrual, as well as increased headcount.

Investment Results

• The total return on the company’s investment portfolio for the three months ended September 30, 2013 was 0.8% compared to 2.2% for the three months ended September 30, 2012.

• The decrease in total return is primarily due to realized and unrealized gains being much lower in the third quarter of 2013 than in the third quarter of 2012.

• See the table below for the components of our investment returns:

(Expressed in millions of U.S. Dollars)	Three months ended September 30,		Nine months ended September 30,
	2013	2012	2013	2012
Net investment income	$                     39.3	$                 39.1	$               110.3	$               128.8
Net realized investment gains (losses)	27.5	149.8	(8.1)	292.0
Change in unrealized losses	-	-	-	(15.4)
Net investment income, realized gains and unrealized gains	$                     66.8	$               188.9	$               102.2	$               405.4
Average invested assets	$                8,522.7	$            8,449.4	$            8,534.9	$            8,332.5
Financial statement portfolio return	0.8%	2.2%	1.2%	4.9%
Note: net investment income, realized gains and unrealized gains are disclosed on a pre-tax basis

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Shareholders’ Equity

• As of September 30, 2013, the company’s total shareholders’ equity was $3,443.9 million, compared to $3,326.3 million as of December 31, 2012.

• As of September 30, 2013, diluted book value per share was $99.16, an increase of 3.1% compared to $96.18 as of June 30, 2013, and an increase of 7.1% compared to $92.59 as of December 31, 2012.

Capital Management

• During the third quarter of 2013, the company repurchased 427,388 of its common shares through its share repurchase program in the open market at an average price of $94.93 per share and an aggregate cost of $40.6 million.

• In May 2013, the company’s shareholders approved a quarterly dividend equal to $0.50 per share. The first dividend was paid on July 3, 2013 to shareholders of record on June 25, 2013 while the second dividend was paid on October 3, 2013 to shareholders of record on September 24, 2013. The two remaining dividends are anticipated to be paid on January 2, 2014 and April 3, 2014.

Supplementary Information

Allied World will be providing a Financial Supplement relating to third quarter 2013 and an Investment Supplement as of September 30, 2013. This information will be available in the “Investor Relations” section of the company’s website at www.awac.com.

Conference Call

Allied World will host a conference call on Thursday, October 24, 2013 at 9:00 a.m. (Eastern Time) to discuss the results for the third quarter ended September 30, 2013. The public may access a live webcast of the conference call at the “Investor Relations” section of the company’s website at www.awac.com. In addition, the conference call can be accessed by dialing (888) 317-6003 (U.S. and Canada callers) or (412) 317-6061 (international callers) and entering the passcode 4405281 approximately ten minutes prior to the call.

Following the conclusion of the presentation, a replay of the call will be available through Friday, November 8, 2013 by dialing (877) 344-7529 (U.S. and Canada callers) or (412) 317-0088 (international callers) and entering the passcode 10034009. In addition, the webcast will remain available online through Friday, November 8, 2013 at www.awac.com.

Non-GAAP Financial Measures

In presenting the company’s results, management has included and discussed in this press release certain non-generally accepted accounting principles (“non-GAAP”) financial measures within the meaning of Regulation G as promulgated by the U.S. Securities and Exchange Commission. Management believes that these non-GAAP measures, which may be defined differently by other companies, better explain the company’s results of operations in a manner that allows for a more complete understanding of the underlying trends in the company’s business. However, these measures should not be viewed as a substitute for those determined in accordance with generally accepted accounting principles (“U.S. GAAP”).

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“Operating income” is an internal performance measure used in the management of the company’s operations and represents after-tax operational results excluding, as applicable, net realized investment gains or losses, net impairment charges recognized in earnings, net foreign exchange gain or loss, and other non-recurring items. The company excludes net realized investment gains or losses, net impairment charges recognized in earnings, net foreign exchange gain or loss, and other non-recurring items from the calculation of operating income because these amounts are heavily influenced by and fluctuate in part according to the availability of market opportunities and other factors. In addition to presenting net income determined in accordance with U.S. GAAP, the company believes that showing operating income enables investors, analysts, rating agencies and other users of the company’s financial information to more easily analyze our results of operations and underlying business performance. Operating income should not be viewed as a substitute for U.S. GAAP net income.

The company has included “diluted book value per share” because it takes into account the effect of dilutive securities; therefore, the company believes it is an important measure of calculating shareholder returns.

“Annualized net income return on average shareholders’ equity” (“ROAE”) is calculated using average shareholders’ equity, excluding the average after tax unrealized gains (or losses) on investments. Unrealized gains (losses) on investments are primarily the result of interest rate and credit spread movements and the resultant impact on fixed income securities. Such gains (losses) are not related to management actions or operational performance, nor are they likely to be realized. Therefore, the company believes that excluding these unrealized gains (losses) provides a more consistent and useful measurement of operating performance, which supplements U.S. GAAP information. In calculating ROAE, the net income (loss) available to shareholders for the period is multiplied by the number of such periods in a calendar year in order to arrive at annualized net income (loss) available to shareholders. The company presents ROAE as a measure that is commonly recognized as a standard of performance by investors, analysts, rating agencies and other users of its financial information.

“Annualized operating return on average shareholders’ equity” is calculated using operating income (as defined above and annualized in the manner described for net income (loss) available to shareholders under ROAE above) and average shareholders’ equity, excluding the average after tax unrealized gains (losses) on investments. Unrealized gains (losses) are excluded from equity for the reasons outlined in the annualized net income return on average shareholders’ equity explanation above.

Reconciliations of these financial measures to their most directly comparable U.S. GAAP measures are included in the attached tables.

About Allied World Assurance Company

Allied World Assurance Company Holdings, AG, through its subsidiaries and brand known as Allied World, is a global provider of innovative property, casualty and specialty insurance and reinsurance solutions. Allied World offers superior

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client service through a global network of offices and branches. All of Allied World’s rated insurance and reinsurance subsidiaries are rated A by A.M. Best Company, A by Standard & Poor’s, and A2 by Moody’s, and our Lloyd’s Syndicate 2232 is rated A+ by Standard & Poor’s and Fitch.

Please visit the following for further information on Allied World: Web: www.awac.com | Facebook: www.facebook.com/alliedworld | LinkedIn: http://www.linkedin.com/company/Allied-World.

Cautionary Statement Regarding Forward-Looking Statements

Any forward-looking statements made in this press release reflect our current views with respect to future events and financial performance and are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Such statements involve risks and uncertainties, which may cause actual results to differ materially from those set forth in these statements. For example, our forward-looking statements could be affected by pricing and policy term trends; increased competition; the adequacy of our loss reserves; negative rating agency actions; greater frequency or severity of unpredictable catastrophic events; the impact of acts of terrorism and acts of war; the company or its subsidiaries becoming subject to significant income taxes in the United States or elsewhere; changes in regulations or tax laws; changes in the availability, cost or quality of reinsurance or retrocessional coverage; adverse general economic conditions; and judicial, legislative, political and other governmental developments, as well as management’s response to these factors, and other factors identified in our filings with the U.S. Securities and Exchange Commission. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date on which they are made. We are under no obligation (and expressly disclaim any such obligation) to update or revise any forward-looking statement that may be made from time to time, whether as a result of new information, future developments or otherwise.

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ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(Expressed in thousands of United States dollars, except share and per share amounts)

	Quarter Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Revenues:
Gross premiums written	$	580,893	$	504,420	$	2,183,174	$	1,832,219
Premiums ceded		(127,816)		(112,883)		(453,823)		(357,019)
Net premiums written		453,077		391,537		1,729,351		1,475,200
Change in unearned premiums		57,696		49,480		(248,079)		(202,546)
Net premiums earned		510,773		441,017		1,481,272		1,272,654
Net investment income		39,271		39,121		110,294		128,781
Net realized investment gains (losses)		27,487		149,813		(8,074)		292,057
Total revenues		577,531		629,951		1,583,492		1,693,492
Expenses:
Net losses and loss expenses		276,970		258,948		807,276		724,530
Acquisition costs		65,114		51,086		186,416		149,812
General and administrative expenses		88,553		78,572		251,818		222,917
Amortization of intangible assets		633		633		1,900		1,900
Interest expense		14,094		13,822		42,416		41,579
Foreign exchange loss (gain)		4,353		1,023		7,361		(77)
Total expenses		449,717		404,084		1,297,187		1,140,661
Income before income taxes		127,814		225,867		286,305		552,831
Income tax expense		4,971		6,220		6,332		18,677
NET INCOME	$	122,843	$	219,647	$	279,973	$	534,154
PER SHARE DATA:
Basic earnings per share	$	3.61	$	6.16	$	8.15	$	14.68
Diluted earnings per share	$	3.54	$	6.00	$	7.97	$	14.28
Weighted average common shares outstanding		33,991,359		35,652,768		34,340,227		36,379,514
Weighted average common shares and common share equivalents outstanding		34,728,193		36,616,734		35,131,092		37,393,093
Dividends paid per share	$	0.500	$	0.750	$	0.875	$	1.500

A dividend of $0.50 was also paid on October 3, 2013 to shareholders of record on September 24, 2013.

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ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS

(Expressed in thousands of United States dollars, except share and per share amounts)

ASSETS:	As of     September 30,     2013		As of     December 31,     2012
Fixed maturity investments trading, at fair value	$	6,047,883	$	6,626,454
Equity securities trading, at fair value		708,929		523,949
Other invested assets		905,025		783,534
Total investments		7,661,837		7,933,937
Cash and cash equivalents		1,210,564		865,364
Insurance balances receivable		740,112		510,532
Funds held		375,131		336,368
Prepaid reinsurance		327,052		277,406
Reinsurance recoverable		1,226,034		1,141,110
Accrued investment income		25,471		29,135
Net deferred acquisition costs		145,951		108,010
Goodwill		268,376		268,376
Intangible assets		49,464		51,365
Balances receivable on sale of investments		237,031		418,879
Net deferred tax assets		41,832		25,580
Other assets		68,665		63,884
Total assets	$	12,377,520	$	12,029,946
LIABILITIES:
Reserve for losses and loss expenses	$	5,780,781	$	5,645,549
Unearned premiums		1,515,746		1,218,021
Reinsurance balances payable		193,643		136,264
Balances due on purchases of investments		497,974		759,934
Senior notes		798,426		798,215
Dividends payable		16,952		—
Accounts payable and accrued liabilities		130,070		145,628
Total liabilities		8,933,592		8,703,611
SHAREHOLDERS’ EQUITY:
Common shares, 2013: par value CHF 12.30 per share and 2012: par value CHF 12.64 per share (2013: 34,972,795; 2012: 36,369,868 shares issued and 2013: 33,814,920; 2012: 34,797,781 shares outstanding)		424,837		454,980
Treasury shares, at cost (2013: 1,157,875; 2012: 1,572,087)		(85,845)		(113,818)
Retained earnings		3,104,936		2,985,173
Total shareholders’ equity		3,443,928		3,326,335
Total liabilities and shareholders’ equity	$	12,377,520	$	12,029,946

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ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG

UNAUDITED CONSOLIDATED SEGMENT DATA

(Expressed in thousands of United States dollars, except for ratio information)

Quarter Ended September 30, 2013	U.S.     Insurance		International   Insurance		Reinsurance		Total
Gross premiums written	$	308,709	$	132,881	$	139,303	$	580,893
Net premiums written		238,792		75,632		138,653		453,077
Net premiums earned		207,602		87,554		215,617		510,773
Net losses and loss expenses		(141,222)		(31,094)		(104,654)		(276,970)
Acquisition costs		(28,426)		282		(36,970)		(65,114)
General and administrative expenses		(41,616)		(26,450)		(20,487)		(88,553)
Underwriting (loss) income		(3,662)		30,292		53,506		80,136
Net investment income								39,271
Net realized investment gains								27,487
Amortization of intangible assets								(633)
Interest expense								(14,094)
Foreign exchange loss								(4,353)
Income before income taxes							$	127,814
GAAP Ratios:
Loss and loss expense ratio		68.0%		35.5%		48.5%		54.2%
Acquisition cost ratio		13.7%		(0.3%)		17.1%		12.7%
General and administrative expense ratio		20.0%		30.2%		9.5%		17.3%
Combined ratio		101.7%		65.4%		75.1%		84.2%
Quarter Ended September 30, 2012	U.S. Insurance		International Insurance		Reinsurance		Total
Gross premiums written	$	263,129	$	121,315	$	119,976	$	504,420
Net premiums written		200,779		71,199		119,559		391,537
Net premiums earned		173,948		85,329		181,740		441,017
Net losses and loss expenses		(109,111)		(15,099)		(134,738)		(258,948)
Acquisition costs		(22,696)		266		(28,656)		(51,086)
General and administrative expenses		(37,388)		(22,920)		(18,264)		(78,572)
Underwriting income		4,753		47,576		82		52,411
Net investment income								39,121
Net realized investment gains								149,813
Amortization of intangible assets								(633)
Interest expense								(13,822)
Foreign exchange loss								(1,023)
Income before income taxes							$	225,867
GAAP Ratios:
Loss and loss expense ratio		62.7%		17.7%		74.1%		58.7%
Acquisition cost ratio		13.0%		(0.3%)		15.8%		11.6%
General and administrative expense ratio		21.5%		26.9%		10.0%		17.8%
Combined ratio		97.2%		44.3%		99.9%		88.1%

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ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG

UNAUDITED CONSOLIDATED SEGMENT DATA

(Expressed in thousands of United States dollars, except for ratio information)

Nine Months Ended September 30, 2013	U.S.     Insurance		International   Insurance		Reinsurance		Total
Gross premiums written	$	872,024	$	453,990	$	857,160	$	2,183,174
Net premiums written		652,464		259,771		817,116		1,729,351
Net premiums earned		593,477		258,809		628,986		1,481,272
Net losses and loss expenses		(398,910)		(90,997)		(317,369)		(807,276)
Acquisition costs		(78,824)		1,489		(109,081)		(186,416)
General and administrative expenses		(119,514)		(75,374)		(56,930)		(251,818)
Underwriting (loss) income		(3,771)		93,927		145,606		235,762
Net investment income								110,294
Net realized investment losses								(8,074)
Amortization of intangible assets								(1,900)
Interest expense								(42,416)
Foreign exchange loss								(7,361)
Income before income taxes							$	286,305
GAAP Ratios:
Loss and loss expense ratio		67.2%		35.2%		50.5%		54.5%
Acquisition cost ratio		13.3%		(0.6%)		17.3%		12.6%
General and administrative expense ratio		20.1%		29.1%		9.1%		17.0%
Combined ratio		100.6%		63.7%		76.9%		84.1%
Nine Months Ended September 30, 2012	U.S. Insurance		International Insurance		Reinsurance		Total
Gross premiums written	$	733,314	$	418,498	$	680,407	$	1,832,219
Net premiums written		551,286		255,150		668,764		1,475,200
Net premiums earned		490,091		247,805		534,758		1,272,654
Net losses and loss expenses		(309,889)		(75,432)		(339,209)		(724,530)
Acquisition costs		(63,918)		1,376		(87,270)		(149,812)
General and administrative expenses		(103,162)		(66,969)		(52,786)		(222,917)
Underwriting income		13,122		106,780		55,493		175,395
Net investment income								128,781
Net realized investment gains								292,057
Amortization of intangible assets								(1,900)
Interest expense								(41,579)
Foreign exchange gain								77
Income before income taxes							$	552,831
GAAP Ratios:
Loss and loss expense ratio		63.2%		30.4%		63.4%		56.9%
Acquisition cost ratio		13.0%		(0.6%)		16.3%		11.8%
General and administrative expense ratio		21.0%		27.0%		9.9%		17.5%
Combined ratio		97.2%		56.8%		89.6%		86.2%

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ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG

UNAUDITED OPERATING INCOME RECONCILIATION

(Expressed in thousands of United States dollars, except share and per share amounts)

	Quarter Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Net income	$	122,843	$	219,647	$	279,973	$	534,154
Add after tax effect of:
Net realized investment (gains) losses		(25,395)		(141,451)		2,160		(276,035)
Foreign exchange loss (gain)		4,353		1,023		7,361		(77)
Operating income	$	101,801	$	79,219	$	289,494	$	258,042
Weighted average common shares outstanding:
Basic		33,991,359		35,652,768		34,340,227		36,379,514
Diluted		34,728,193		36,616,734		35,131,092		37,393,093
Basic per share data:
Net income	$	3.61	$	6.16	$	8.15	$	14.68
Add after tax effect of:
Net realized investment (gains) losses		(0.75)		(3.97)		0.06		(7.59)
Foreign exchange loss (gain)		0.13		0.03		0.22		—
Operating income	$	2.99	$	2.22	$	8.43	$	7.09
Diluted per share data:
Net income	$	3.54	$	6.00	$	7.97	$	14.28
Add after tax effect of:
Net realized investment (gains) losses		(0.73)		(3.86)		0.06		(7.38)
Foreign exchange loss (gain)		0.12		0.02		0.21		—
Operating income	$	2.93	$	2.16	$	8.24	$	6.90

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ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG

UNAUDITED DILUTED BOOK VALUE PER SHARE RECONCILIATION

(Expressed in thousands of United States dollars, except share and per share amounts)

	As of   September 30,   2013		As of   December 31,   2012		As of   September 30,   2012
Price per share at period end	$	99.39	$	78.80	$	77.25
Total shareholders’ equity	$	3,443,928	$	3,326,335	$	3,435,786
Basic common shares outstanding		33,814,920		34,797,781		35,402,558
Add: unvested restricted share units		83,240		135,123		179,986
Add: performance based equity awards		270,853		485,973		508,130
Add: employee share purchase plan		15,320		10,750		5,925
Add: dilutive options/warrants outstanding		1,050,832		1,224,607		1,306,837
Weighted average exercise price per share	$	47.77	$	47.02	$	46.14
Deduct: options bought back via treasury method		(505,057)		(730,652)		(780,502)
Common shares and common share equivalents outstanding		34,730,108		35,923,582		36,622,934
Basic book value per common share	$	101.85	$	95.59	$	97.05
Diluted book value per common share	$	99.16	$	92.59	$	93.82

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ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG

UNAUDITED ANNUALIZED RETURN ON SHAREHOLDERS’ EQUITY RECONCILIATION

(Expressed in thousands of United States dollars, except for percentage information)

	Quarter Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Opening shareholders’ equity	$	3,373,229	$	3,283,901	$	3,326,335	$	3,149,022
Deduct: accumulated other comprehensive income		—		(1,414)		—		(14,484)
Adjusted opening shareholders’ equity		3,373,229		3,282,487		3,326,335		3,134,538
Closing shareholders’ equity	$	3,443,928	$	3,435,786	$	3,443,928	$	3,435,786
Deduct: accumulated other comprehensive income		—		(1,385)		—		(1,385)
Adjusted closing shareholders’ equity		3,443,928		3,434,401		3,443,928		3,434,401
Average shareholders’ equity	$	3,408,579	$	3,358,444	$	3,385,132	$	3,284,470
Net income available to shareholders	$	122,843	$	219,647	$	279,973	$	534,154
Annualized net income available to shareholders		491,372		878,588		373,297		712,205
Annualized return on average shareholders’ equity - net income available to shareholders		14.4%		26.2%		11.0%		21.7%
Operating income available to shareholders	$	101,801	$	79,219	$	289,494	$	258,042
Annualized operating income available to shareholders		407,204		316,876		385,992		344,056
Annualized return on average shareholders’ equity - operating income available to shareholders		11.9%		9.4%		11.4%		10.5%

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Media:

Noelle Campbell

Manager, Corporate Communications

+1-646-794-0544

Noelle.campbell@awacservices.com

OR

Faye Cook

SVP, Marketing & Communications

+1-441-278-5406

Faye.cook@awac.com

Investors:

Sarah Doran

SVP, Investor Relations and Treasurer

+1-646-794-0590

Sarah.doran@awac.com

Website: www.awac.com

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