Earnings Per Share

We calculate basic earnings per share by dividing net income available to common stockholders by the weighted average number of common shares outstanding during the period. Diluted earnings per share further includes the dilutive effect of stock-based compensation awards. We calculate that dilutive effect using the “treasury stock method” (as defined by GAAP).

The following table presents information concerning basic and diluted earnings per share:



	Three Months Ended				Nine Months Ended
	January 31,				January 31,
(Dollars in millions, except per share amounts)	2017		2018		2017		2018
Net income available to common stockholders	$	182	$	190	$	524	$	607

Share data (in thousands):
Basic average common shares outstanding	480,650		480,361		486,105		480,193
Dilutive effect of stock-based awards	3,308		3,883		3,515		3,318
Diluted average common shares outstanding	483,958		484,244		489,620		483,511

Basic earnings per share	$	0.38	$	0.39	$	1.08	$	1.26
Diluted earnings per share	$	0.38	$	0.39	$	1.07	$	1.25

We excluded common stock-based awards for approximately 2,789,000 shares and 0 shares from the calculation of diluted earnings per share for the three months ended January 31, 2017 and 2018, respectively. We excluded common stock-based awards for approximately 2,225,000 shares and 1,073,000 shares from the calculation of diluted earnings per share for the nine months ended January 31, 2017 and 2018, respectively. We excluded those awards because they were not dilutive for those periods under the treasury stock method.