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STOCK COMPENSATION (Tables) | 12 Months Ended
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Dec. 31, 2021
Share-based Payment Arrangement [Abstract] |
Schedule of employees participating in stock-based compensation programs | At December 31, 2021, the number of current and former employees participating in stock-based compensation programs for the Registrants was as follows:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
Number of employees | 1,728 |  | 241 |  | 271 |  | 70 |  | 45 |  | 173 |
Assumptions used in the pricing model and the weighted average grant-date fair value of performance share award units granted | The following table shows the assumptions used in the pricing model and the weighted average grant-date fair value of TSR awards granted:
Year Ended December 31 | 2021 |  | 2020 |  | 2019
Expected volatility | 30.0% |  | 15.4% |  | 15.6%
Expected term (in years) | 3 |  | 3 |  | 3
Interest rate | 0.2% |  | 1.4% |  | 2.4%
Weighted average grant-date fair value | $69.06 |  | $77.65 |  | $62.71
Schedule of compensation costs and related tax benefits | Total PSU compensation cost, and the related tax benefit recognized in income, for the years ended December 31, 2021, 2020, and 2019 are as follows:
| 2021 |  | 2020 |  | 2019
| (in millions)
Southern Company |  |  |  |  |
Compensation cost recognized in income | $ | 112 |  |  | $ | 84 |  |  | $ | 77 |
Tax benefit of compensation cost recognized in income | 29 |  |  | 22 |  |  | 20 |
Southern Company Gas |  |  |  |  |
Compensation cost recognized in income | $ | 17 |  |  | $ | 13 |  |  | $ | 14 |
Tax benefit of compensation cost recognized in income | 4 |  |  | 4 |  |  | 4 |
Total intrinsic value of options exercised, and the related tax benefit, for the years ended December 31, 2021, 2020, and 2019 are presented below:
Year Ended December 31 | 2021 |  | 2020 |  | 2019
| (in millions)
Southern Company |  |  |  |  |
Intrinsic value of options exercised | $ | 34 |  |  | $ | 38 |  |  | $ | 167 |
Tax benefit of options exercised | 7 |  |  | 9 |  |  | 35 |
Alabama Power |  |  |  |  |
Intrinsic value of options exercised | $ | 3 |  |  | $ | 5 |  |  | $ | 21 |
Tax benefit of options exercised | 1 |  |  | 1 |  |  | 4 |
Georgia Power |  |  |  |  |
Intrinsic value of options exercised | $ | 14 |  |  | $ | 9 |  |  | $ | 30 |
Tax benefit of options exercised | 3 |  |  | 2 |  |  | 6 |
Share-based compensation, stock options, activity | Southern Company's activity in the stock option program for 2021 is summarized below:
| Shares Subject to Option |  | Weighted Average Exercise Price
| (in millions) |  |
Outstanding at December 31, 2020 | 4.3 |  |  | $ | 43.04 |
Exercised | 1.5 |  |  | 43.21 |
Outstanding and Exercisable at December 31, 2021 | 2.8 |  |  | $ | 42.95 |
Schedule of aggregate and total intrinsic value of options exercised | At December 31, 2021, the aggregate intrinsic value for the options outstanding and exercisable was as follows:
| Southern Company |  | Georgia Power |  | Southern Company Gas
| (in millions)
Total intrinsic value for outstanding and exercisable options | $ | 71 |  |  | $ | 17 |  |  | $ | 8 |

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