Earnings Per Common Share

The following is a reconciliation of the numerators and denominators of the basic and diluted earnings per common share computations for the years ended December 31, 2017, 2016 and 2015 (in millions, except per share amounts):



	Year Ended December 31,
	2017		2016		2015
Basic:
Net income attributable to Intercontinental Exchange, Inc.	$	2,514	$	1,422	$	1,274
Weighted average common shares outstanding	589		595		556
Basic earnings per common share	$	4.27	$	2.39	$	2.29
Diluted:
Weighted average common shares outstanding	589		595		556
Effect of dilutive securities - stock options and restricted stock	5		4		3
Diluted weighted average common shares outstanding	594		599		559
Diluted earnings per common share	$	4.23	$	2.37	$	2.28

Basic earnings per common share is calculated using the weighted average common shares outstanding during the periods. The weighted average common shares outstanding decreased for the year ended December 31, 2017, from the prior year period, primarily due to stock repurchases during 2017 (Note 11). The weighted average common shares outstanding increased for the year ended December 31, 2016, over the prior year period, primarily due to stock issued for the Interactive Data and Trayport acquisitions, partially offset by stock repurchases. We issued 32.3 million shares of our common stock to Interactive Data stockholders and 12.6 million shares of our common stock to Trayport stockholders, which are weighted to show these additional shares outstanding for periods after the respective acquisition dates (Note 3).

Common equivalent shares from stock options and restricted stock awards, using the treasury stock method, are included in the diluted per share calculations unless the effect of their inclusion would be antidilutive. During the years ended December 31, 2017, 2016 and 2015, 694,343, 724,918 and 836,405 outstanding stock options, respectively, were not included in the computation of diluted earnings per common share, because to do so would have had an antidilutive effect. As of December 31, 2017 and 2016, there were 88,930 and 110,265 restricted stock units, respectively, that were vested but have not been issued that are included in the computation of basic and diluted earnings per share. Certain figures in the table above may not recalculate due to rounding.