EARNINGS PER SHARE

Basic earnings per share are based upon the weighted-average number of shares of common stock outstanding. Diluted earnings per share are based upon the weighted-average number of shares of common stock outstanding, plus all potentially dilutive securities that were assumed to be converted into common shares at the beginning of the period under the treasury stock method. Our potentially dilutive securities consist of restricted stock, restricted stock units, performance share awards and SSARs.



Share amounts in millions	Quarter Ended March 31,
Share amounts in millions	2018	2017
Denominator for basic earnings per share:
Weighted average common shares outstanding - basic	144.7	144.2
Effect of dilutive securities:
Dilutive effect of employee stock plans	2.0	1.7
Denominator for diluted earnings per share:
Weighted average shares outstanding - diluted	146.7	145.9

For the quarter ended March 31, 2018, there were no restricted stock (shares or units), performance share awards and SSARs that were considered not in-the-money for purposes of our earnings per share calculation.

For the quarter ended March 31, 2017, restricted stock (shares or units), performance share awards and SSARs relating to approximately 0.6 million shares of our common stock were considered not in-the-money for purposes of our earnings per share calculation.