13. Net (Loss) Income per Share Attributable to Common Stock

Net loss per share attributable to common stock is calculated using the two-class method. The two-class method is an allocation method of calculating loss per share when a company’s capital structure includes participating securities that have rights to undistributed earnings. Historically, the Company’s employees and officers that held unvested restricted stock were entitled to dividends when the Company paid dividends (“participating”). The Company’s employees and officers that hold unvested restricted stock awarded during 2016 or thereafter are not entitled to dividends when the Company pays dividends (“non-participating”). The Company’s basic net loss per share attributable to common stock is computed by reducing the Company’s net loss by the income allocable to unvested restricted stockholders that have a right to participate in earnings. The Company’s employees and officers that hold unvested restricted stock do not participate in losses because they are not contractually obligated to do so. The undistributed earnings are allocated based on the relative percentage of the weighted average unvested participating restricted stock awards. The basic net loss per share attributable to common stock is computed by dividing the net loss attributable to common stock by the weighted average shares outstanding. The weighted average shares outstanding for the year ended December 31, 2015 was calculated by totaling (i) the product of (x) the weighted shares of Legacy Dawson Common Stock outstanding at the beginning of the year multiplied by (y) the Exchange Ratio, plus (ii) the number of shares associated with awards of Legacy Dawson participating restricted stock and restricted stock units that vested in conjunction with the Merger, weighted as of February 11, 2015, plus (iii) the number of shares of Legacy TGC Common Stock outstanding immediately prior to the Merger, weighted to reflect that such shares were outstanding from February 11, 2015 until December 31, 2015. The Company’s diluted loss per share attributable to common stock is computed by adjusting basic loss per share attributable to common stock by income allocable to unvested participating restricted stock, if any, divided by weighted average diluted shares outstanding.

A reconciliation of the loss per share attributable to common stock is as follows (in thousands, except share and per share data):


	Year Ended December 31,
	2017		2016		2015
Net loss	$	(31,266)	$	(39,792)	$	(26,279)
Income allocable to unvested participating restricted stock		—		—		—
Basic loss attributable to common stock	$	(31,266)	$	(39,792)	$	(26,279)
Reallocation of participating earnings		—		—		—
Diluted loss attributable to common stock	$	(31,266)	$	(39,792)	$	(26,279)
Weighted average common shares outstanding:
Basic		21,694,645		21,611,562		20,688,185
Dilutive common stock options, restricted stock unit awards and non-participating restricted stock awards		—		—		—
Diluted		21,694,645		21,611,562		20,688,185
Basic loss attributable to a share of common stock	$	(1.44)	$	(1.84)	$	(1.27)
Diluted loss attributable to a share of common stock	$	(1.44)	$	(1.84)	$	(1.27)

The Company had a net loss in the years ended December 31, 2017, 2016 and 2015. As a result, all stock options, restricted stock unit awards, and non-participating restricted stock awards were anti-dilutive and excluded from weighted average shares used in determining the diluted loss attributable to a share of common stock for the respective periods. The following weighted average numbers of stock options, restricted stock unit awards, and non-participating restricted stock awards have been excluded from the calculation of diluted loss per share attributable to common stock, as their effect would be anti-dilutive for the years ended December 31, 2017, 2016 and 2015:


	Year Ended December 31,
		2017	2016	2015
Stock options		338,355	411,763	425,981
Restricted stock unit awards		332,221	268,461	126,596
Non-participating restricted stock awards		73,296	76,303	—
Total		743,872	756,527	552,577

The Company has not awarded participating restricted stock for the years ended December 31, 2017, 2016 and 2015.