8. Earnings (Loss) Per Share

Basic earnings (loss) per share is computed on the basis of weighted average outstanding common shares. Diluted earnings (loss) per share is computed on the basis of basic weighted average outstanding common shares adjusted for the dilutive effect of stock options and other outstanding dilutive securities.

The following table reconciles the average share amounts used to compute both basic and diluted earnings (loss) per share (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Weighted average shares outstanding:
Basic weighted average shares outstanding		118,254		116,118		117,096		117,606
Add: Dilutive effect of stock options		1,489		—		—		1,365

Diluted weighted average shares outstanding		119,743		116,118		117,096		118,971

The diluted earnings (loss) per share computation excludes 3.3 million and 10.1 million options to purchase shares, contingently issuable shares and restricted share awards during the three and nine months ended September 30, 2017, respectively, as their effect would be anti-dilutive. The diluted earnings (loss) per share computation excludes 9.9 million and 6.1 million options to purchase shares, restricted share awards, and contingently issuable shares during the three and nine months ended September 30, 2016, respectively, as their effect would be anti-dilutive.

Common stock outstanding as of September 30, 2017 and December 31, 2016 was 118,293,967 and 117,336,797, respectively.