Table:
| Years ended December 31, |  |  |  |
| --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 |
| Basic weighted-average shares outstanding | 103.9 | 103.2 | 102.2 |
| Effect of potential common stock: |  |  |  |
| Common stock awards | 1.2 | 1.2 | 1.3 |
| Diluted weighted-average shares outstanding | 105.1 | 104.4 | 103.5 |
Paragraphs:
Earnings per Share—Basic earnings per share were calculated using net earnings and the weighted-average number of shares of common stock outstanding during the respective year. Diluted earnings per share were calculated using net earnings and the weighted-average number of shares of common stock and potential common stock associated with stock options outstanding during the respective year. The effects of potential common stock were determined using the treasury stock method:
As of and for the years ended December 31, 2019, 2018 and 2017, there were 0.627, 0.724 and 0.478 outstanding stock options, respectively, that were not included in the determination of diluted earnings per share because doing so would have been antidilutive.
Question:
How are the effects of potential common stock determined?
Answer: using the treasury stock method