Note 20. Quarterly Financial Data (Unaudited)

The following is a summary of the unaudited quarterly results of operations for the years ended December 31, 2017 and 2016 (in thousands, except per share amounts).

	2017
	March 31,			June 30,			September 30,			December 31,
Revenue	$	241,459		$	211,016		$	207,723		$	195,142
Operating expenses		192,766			188,120			184,723			189,975
Gross margin		48,693			22,896			23,000			5,167
Corporate general and administrative expenses		8,768			9,232			7,979			7,316
Operating income (loss)		39,925			13,664			15,021			(2,149	)
Other income:
Interest expense		(1,517	)		(1,692	)		(1,777	)		(1,689	)
Gain on sale of operations, net		22			23			-			-
Other income, net		2,737			3,764			2,792			5,196
Total other income, net		1,242			2,095			1,015			3,507
Income from continuing operations before income tax expense		41,167			15,759			16,036			1,358
Income tax expense (benefit)		16,141			4,343			6,172			(3,368	)
Income from continuing operations		25,026			11,416			9,864			4,726
(Loss) gain from operations of discontinued operations, net of tax		(152	)		(418	)		(206	)		121
Net income	$	24,874		$	10,998		$	9,658		$	4,847
Earnings (loss) per share:
Basic:
Continuing operations	$	0.47		$	0.21		$	0.18		$	0.09
Discontinued operations		—			(0.01	)		—			—
Net income	$	0.47		$	0.20		$	0.18		$	0.09
Diluted:
Continuing operations	$	0.45		$	0.20		$	0.18		$	0.08
Discontinued operations		—			(0.01	)		—			—
Net income	$	0.45		$	0.19		$	0.18		$	0.08
Basic weighted average common shares		53,293			53,968			54,142			54,034
Diluted weighted average common shares		55,214			55,831			55,827			55,822

	2016
	March 31,			June 30,			September 30,			December 31,
Revenue	$	224,238		$	197,015		$	199,794		$	178,785
Operating expenses		178,117			173,996			174,069			171,544
Gross margin		46,121			23,019			25,725			7,241
Corporate general and administrative expenses		10,245			8,346			8,679			9,049
Operating income (loss)		35,876			14,673			17,046			(1,808	)
Other income (expense):
Interest expense		(1,526	)		(1,733	)		(1,760	)		(1,574	)
Gain on sale of operations, net		101			50			329			375
Other income, net		2,147			703			2,632			1,475
Total other income (expense), net		722			(980	)		1,201			276
Income (loss) from continuing operations before income tax expense (benefit)		36,598			13,693			18,247			(1,532	)
Income tax expense (benefit)		14,800			5,306			7,260			(967	)
Income (loss) from continuing operations		21,798			8,387			10,987			(565	)
Loss from operations of discontinued operations, net of tax		(30	)		(258	)		(133	)		(121	)
Net income (loss)	$	21,768		$	8,129		$	10,854		$	(686	)
Earnings (loss) per share:
Basic:
Continuing operations	$	0.42		$	0.16		$	0.21		$	(0.01	)
Discontinued operations		—			—			—			—
Net income (loss)	$	0.42		$	0.16		$	0.21		$	(0.01	)
Diluted:
Continuing operations	$	0.41		$	0.16		$	0.20		$	(0.01	)
Discontinued operations		—			—			—			—
Net income (loss)	$	0.41		$	0.16		$	0.20		$	(0.01	)
Basic weighted average common shares		51,572			52,031			52,648			53,019
Diluted weighted average common shares		52,745			53,079			53,846			53,019