Earnings per Share

3 Months Ended

Mar. 31, 2021

Basic earnings per share is calculated by dividing net income by the weighted average number of shares outstanding during the reported period. The calculation of diluted earnings per share is similar to basic earnings per share, except that the weighted average number of shares outstanding includes the dilution from potential shares resulting from stock options, restricted stock awards and other stock awards. The components of basic and diluted earnings per share are as follows:


	Three Months Ended March 31,
In millions, except per share amounts	2021		2020
Net income attributable to common stockholders	$	53	$	168
Weighted average outstanding shares of common stock	108.7		110.3
Dilutive effect of employee stock options, restricted stock and other stock awards	4.1		1.0
Common stock and common stock equivalents	112.8		111.3
Net income per share:
Basic	$	0.49	$	1.52
Diluted	$	0.47	$	1.51

Options to purchase 1.2 million shares of common stock for the three months ended March 31, 2021 and 2.2 million shares of common stock for the three months ended March 31, 2020 were not included in the computation of diluted earnings per share because the exercise prices of these options were greater than the average market price of the common shares for the period, and therefore would have been anti-dilutive.