13. Earnings Per Share

Basic earnings (loss) per share is computed as net earnings (loss) divided by the basic weighted average common shares outstanding of 35.1 million, 34.4 million and 34.0 million for the year ended December 31, 2017, 2016 and 2015, respectively. The calculation of diluted earnings (loss) per share includes the effect of any dilutive equity incentive instruments. The Company uses the treasury stock method to calculate the effect of outstanding dilutive equity incentive instruments, which requires the Company to compute total proceeds as the sum of the amount the employee must pay upon exercise of the award and the amount of unearned stock-based compensation costs attributable to future services.

Equity incentive instruments for which the total employee proceeds from exercise exceed the average fair value of the same equity incentive instrument over the period have an anti-dilutive effect on earnings per share during periods with net earnings, and accordingly, the Company excludes them from the calculation. Anti-dilutive equity instruments of approximately 36,300 common shares were excluded from the computation of diluted net earnings per share for the year ended December 31, 2017. Due to the net loss incurred during the year ended December 31, 2016 and 2015, the assumed exercise of all equity incentive instruments was anti-dilutive and, therefore, not included in the diluted loss per share calculation for these periods.

The following is a reconciliation of the average shares outstanding used to compute basic and diluted earnings per share:

	2017		2016		2015
Basic weighted average common shares outstanding		35,111,594		34,441,777		34,009,048
Effect of dilutive securities - stock awards		743,308		—		—
Diluted weighted average common shares outstanding		35,854,902		34,441,777		34,009,048