Earnings Per Share and Equity (Exelon)

Earnings per Share

Basic earnings per share is computed by dividing net income attributable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted earnings per share is computed by dividing net income attributable to common shareholders by the weighted average number of common shares outstanding, including the effect of issuing common stock assuming (i) stock options are exercised, and (ii) performance share awards and restricted stock awards are fully vested under the treasury stock method.

The following table sets forth the components of basic and diluted earnings per share and shows the effect of these stock options, performance share awards and restricted stock awards on the weighted average number of shares outstanding used in calculating diluted earnings per share:



	Three Months Ended March 31,
	2018		2017
Exelon
Net income attributable to common shareholders	$	585	$	990
Weighted average common shares outstanding — basic	966		928
Assumed exercise and/or distributions of stock-based awards	2		2
Weighted average common shares outstanding — diluted	968		930

The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 5 million and 9 million for the three months ended March 31, 2018 and 2017, respectively. There were no equity units related to the PHI Merger not included in the calculation of diluted common shares outstanding due to their antidilutive effect for the three months ended March 31, 2018 and 2017. Refer to Note 19 — Shareholders' Equity of the Exelon 2017 Form 10-K for further information regarding the equity units.

Under share repurchase programs, 2 million shares of common stock are held as treasury stock with a cost of $123 million as of March 31, 2018.