Earnings per Share

The denominator for basic and diluted earnings per share for the three and nine months ended September 30, 2017 and 2016 is as follows:



	Three Months Ended September 30		Nine Months Ended September 30
	2017	2016	2017	2016
Denominator for basic earnings per share – weighted-average shares	260.5	263.2	263.2	262.7
Effect of dilutive securities – employee stock options, nonvested restricted stock awards and convertible debentures	6.5	4.9	6.2	5.2
Denominator for diluted earnings per share	267.0	268.1	269.4	267.9

During the three months ended September 30, 2016, weighted-average shares related to certain stock options of 2.5 were excluded from the denominator for diluted earnings per share because the stock options were anti-dilutive. During the nine months ended September 30, 2017 and 2016, weighted-average shares related to certain stock options of 0.5 and 2.3, respectively, were excluded from the denominator for diluted earnings per share because the stock options were anti-dilutive. The Equity Units are potentially dilutive securities but were excluded from the denominator for diluted earnings per share for the three and nine months ended September 30, 2017 and 2016 as the dilutive stock price threshold was not met.

During the three and nine months ended September 30, 2017, we issued approximately 0.2 and 0.8 restricted stock units under our stock incentive plans, 0.4 of which vesting is contingent upon us meeting specified annual earnings targets for the three year period of 2017 through 2019. During the nine months ended September 30, 2016, we issued approximately 1.0 restricted stock units under our stock incentive plans, 0.5 of which vesting is contingent upon us meeting specified annual earnings targets for the three year period of 2016 through 2018. We did not issue any material amounts of restricted stock units under our stock incentive plans during the three months ended September 30, 2016. The contingent restricted stock units have been excluded from the denominator for diluted earnings per share and are included only if and when the contingency is met.