16. Earnings Per Share of Common Stock: The following tables provide the computation of basic and diluted earnings per share of common stock for the three months ended March 31, 2019 and 2018.

	For the Three Months Ended
	March 31, 2019			March 31, 2018
Number of shares on which basic earnings per share is calculated:
Weighted-average shares outstanding during period	889,581,542			920,680,222
Add — Incremental shares under stock-based compensation plans	3,372,460			3,553,104
Add — Incremental shares associated with contingently issuable shares	956,524			1,176,108

Number of shares on which diluted earnings per share is calculated	893,910,526			925,409,434


Income from continuing operations (millions)	$	1,593		$	1,675
Income/(loss) from discontinued operations, net of tax (millions)	(2		)	4

Net income on which basic earnings per share is calculated (millions)	$	1,591		$	1,679


Income from continuing operations (millions)	$	1,593		$	1,675
Net income applicable to contingently issuable shares (millions)	—			—

Income from continuing operations on which diluted earnings per share is calculated (millions)	$	1,593		$	1,675
Income/(loss) from discontinued operations, net of tax, on which basic and diluted earnings per share is calculated (millions)	(2		)	4

Net income on which diluted earnings per share is calculated (millions)	$	1,591		$	1,679


Earnings/(loss) per share of common stock:
Assuming dilution
Continuing operations	$	1.78		$	1.81
Discontinued operations	0.00			0.00

Total	$	1.78		$	1.81

Basic
Continuing operations	$	1.79		$	1.82
Discontinued operations	0.00			0.00

Total	$	1.79		$	1.82

Stock options to purchase 1,137,019 shares and 16,869 shares were outstanding as of March 31, 2019 and 2018, respectively, but were not included in the computation of diluted earnings per share because the options’ exercise price during the respective period was greater than the average market price of the common shares, and, therefore, the effect would have been antidilutive.