Income per Share

12 Months Ended

Dec. 31, 2020

Basic income or loss per share is based on the weighted average number of common shares outstanding during the period. Diluted income per share includes additional common shares that would have been outstanding if potential common shares with a dilutive effect had been issued. Antidilutive securities represent potentially dilutive securities which are excluded from the computation of diluted income or loss per share as their impact was antidilutive.

A reconciliation of the number of shares used for the basic and diluted income per share computations is as follows:


	Year Ended December 31
Millions of shares	2020	2019	2018
Basic weighted average common shares outstanding	881	875	875
Dilutive effect of awards granted under our stock incentive plans	—	—	2
Diluted weighted average common shares outstanding	881	875	877
Antidilutive shares:
Options with exercise price greater than the average market price	27	24	14
Options which are antidilutive due to net loss position	1	1	—
Total antidilutive shares	28	25	14