Basic earnings per share (EPS) amounts are computed by dividing Net income (loss) attributable to Alcoa Corporation by the average number of common shares outstanding. Diluted EPS amounts assume the issuance of common stock for all potentially dilutive share equivalents outstanding.

The share information used to compute basic and diluted EPS attributable to Alcoa Corporation common shareholders was as follows (in millions):

	2018		2017		2016
Average shares outstanding—basic		186		184		183
Effect of dilutive securities:
Stock options		1		1		—
Stock units		2		2		—
Average shares outstanding—diluted		189		187		183

Options to purchase 1 million shares of common stock outstanding as of December 31, 2018 at a weighted average exercise price of $38.67 per share were not included in the computation of diluted EPS because the exercise prices of these options were greater than the average market price of Alcoa Corporation’s common stock.

In 2016, basic average shares outstanding and diluted average shares outstanding were the same because the effect of potential shares of common stock was anti-dilutive. Options to purchase 1 million shares of common stock outstanding as of December 31, 2016 at a weighted average exercise price of $33.05 per share were not included in the computation of diluted EPS because the exercise prices of these options were greater than the average market price of Alcoa Corporation’s common stock. Additionally, 1 million stock units and stock options combined were not included in the computation of diluted EPS because Alcoa Corporation generated a net loss. Had Alcoa Corporation generated net income in 2016, 1 million potential shares of common stock related to stock units and stock options combined would have been included in diluted average shares outstanding.