Item 6. SELECTED FINANCIAL DATA

(Dollars in millions, except per share amounts)

Earnings data for the years ended December 31,	2017			2016			2015			2014			2013
Operating revenues	$	7,190		$	6,555		$	6,188		$	6,165		$	5,585
Operating income		624			721			716			632			577
Net earnings		686			432			427			375			342
Basic earnings per share		6.24			3.84			3.69			3.20			2.92
Diluted earnings per share		6.18			3.81			3.66			3.16			2.87
Cash dividends per share		0.92			0.88			0.84			0.80			0.45
Operating expenses as a percentage of operating revenues:
Rents and purchased transportation		50.8	%		49.7	%		48.4	%		50.0	%		50.2	%
Salaries, wages and employee benefits		22.4			22.4			22.5			20.9			20.4
Depreciation and amortization		5.3			5.5			5.5			4.8			4.5
Fuel and fuel taxes		4.8			4.3			5.1			7.4			8.2
Operating supplies and expenses		3.6			3.6			3.6			3.5			3.6
General and administrative expenses, net of asset dispositions		1.8			1.3			1.1			0.8			0.8
Insurance and claims		1.7			1.2			1.2			1.3			1.0
Operating taxes and licenses		0.6			0.7			0.7			0.7			0.7
Communication and utilities		0.3			0.3			0.3			0.4			0.3
Total operating expenses		91.3			89.0			88.4			89.8			89.7
Operating income		8.7			11.0			11.6			10.2			10.3
Net interest expense		0.4			0.4			0.4			0.4			0.4
Earnings before income taxes		8.3			10.6			11.2			9.8			9.9
Income taxes		(1.2	)		4.0			4.3			3.7			3.8
Net earnings		9.5	%		6.6	%		6.9	%		6.1	%		6.1	%

Balance sheet data as of December 31,	2017			2016			2015			2014			2013
Working capital ratio		1.52			1.65			1.61			1.11			0.96
Total assets (millions)	$	4,465		$	3,951		$	3,630		$	3,374		$	2,818
Stockholders’ equity (millions)	$	1,839		$	1,414		$	1,300		$	1,205		$	1,012
Current portion of long-term debt (millions)		-			-			-		$	250		$	250
Total debt (millions)	$	1,086		$	986		$	998		$	929		$	707
Total debt to equity		0.59			0.70			0.77			0.77			0.70
Total debt as a percentage of total capital		37	%		41	%		43	%		44	%		41	%