BASIC AND DILUTED LOSS PER COMMON SHARE

The following is a reconciliation of weighted average shares outstanding for the years ended December 31, 2017, 2016, 2015, respectively:



	Years Ended December 31,
	2017	2016	2015
Issued common shares at beginning of period	66,205,153	46,519,132	19,677,552
Effect of share options exercised	—	3,471	22,938
Effect of shares issued for settlement of vesting of restricted share units	831,393	196,242	—
Effect of shares issued for exercise of share purchase warrants	—	—	173
Effect of shares issued in business combinations	—	—	13,654,488
Effect of shares issued in asset acquisitions	—	3,184,175	—
Effect of shares issued in public offerings	3,822,561	6,538,038	28,821
Weighted average shares outstanding	70,859,107	56,441,058	33,383,972

Basic and diluted loss per share

The calculation of diluted earnings per share after adjustment for the effects of all potential dilutive common shares, calculated as follows:



	Years Ended December 31,
	2017			2016			2015
Net loss	$	(27,766	)	$	(39,413	)	$	(82,217	)
Basic and diluted weighted average number
of common shares outstanding	70,859,107			56,441,058			33,383,972
Loss per common share	$	(0.39	)	$	(0.70	)	$	(2.46	)

For the three years ended December 31, 2017, 2016 and 2015, 8.71 million, 10.19 million and 5.21 million options and warrants, respectively, and the potential conversion of the debentures have been excluded from the calculation as their effect would have been anti-dilutive.