NET INCOME PER SHARE ATTRIBUTABLE TO GILEAD COMMON STOCKHOLDERS

Basic net income per share attributable to Gilead common stockholders is calculated based on the weighted-average number of shares of our common stock outstanding during the period. Diluted net income per share attributable to Gilead common stockholders is calculated based on the weighted-average number of shares of our common stock and other dilutive securities outstanding during the period. The potentially dilutive shares of our common stock resulting from the assumed exercise of outstanding stock options and equivalents were determined under the treasury stock method.

Potential shares of common stock excluded from the computation of diluted net income per share attributable to Gilead common stockholders because their effect would have been antidilutive were 16 million and 12 million shares for the three months ended March 31, 2019 and 2018, respectively.

The following table summarizes the calculation of basic and diluted net income per share attributable to Gilead common stockholders (in millions, except per share amounts):



	Three Months Ended
	March 31,
	2019		2018
Net income attributable to Gilead	$	1,975	$	1,538
Shares used in per share calculation - basic	1,276		1,307
Dilutive effect of stock options and equivalents	7		13
Shares used in per share calculation - diluted	1,283		1,320
Net income per share attributable to Gilead common stockholders - basic	$	1.55	$	1.18
Net income per share attributable to Gilead common stockholders - diluted	$	1.54	$	1.17