Earnings Per Share

12 Months Ended

Dec. 31, 2020

Earnings per Share

The denominator for basic and diluted earnings per share at December 31, 2020, 2019 and 2018 is as follows:


	2020	2019	2018
Denominator for basic earnings per share—weighted-average shares	250.8	255.5	258.1
Effect of dilutive securities—employee stock options, non-vested restricted stock awards, convertible debentures and equity units	3.5	4.8	6.1
Denominator for diluted earnings per share	254.3	260.3	264.2

During the years ended December 31, 2020, 2019 and 2018, weighted-average shares related to certain stock options of 1.2, 0.6 and 0.3, respectively, were excluded from the denominator for diluted earnings per share because the stock options were anti-dilutive. The Equity Unit purchase contracts were settled in May 2018, and approximately 6.0 shares of our common stock were issued and included in the basic earnings per share calculation.

During the years ended December 31, 2020, 2019 and 2018, we issued approximately 0.3, 0.2 and 0.3 restricted stock units, respectively, of which vesting was contingent upon us meeting certain earnings targets. Contingent restricted stock units are excluded from the denominator for diluted earnings per share and are included only if and when the contingency is met. The 2020 contingent restricted stock units are being measured over the three year period of 2020 through 2022, the 2019 contingent restricted stock units are being measured over the three year period of 2019 through 2021 and the 2018 contingent restricted stock units are being measured over the three year period of 2018 through 2020. Contingent restricted stock units generally vest in March of the year following each measurement period.