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## Note 11 - Stock-Based Compensation - Continued 

Cash-settled RSUs vest over a one to three-year service period, beginning at the date of grant, and the compensation cost is recognized ratably during the vesting period. Forfeitable dividends on cash-settled RSUs are accrued in the form of cash. Compensation cost for cash-settled RSUs subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period. 

The amount payable per unit awarded is equal to the price per share of Unum Group's common stock at settlement of the award, and as such, we measure the value of the award each reporting period based on the current stock price. The effects of changes in the stock price during the service period are recognized as compensation cost over the service period. Changes in the amount of the liability due to stock price changes after the service period are recognized as compensation cost during the period in which the changes occur. At December 31, 2020, we had $1.1 million of unrecognized compensation cost related to cash-settled RSUs that will be recognized over a weighted average period of 1.1 years. 

The cash-settled RSUs have a weighted average grant date fair value per unit granted of $22.94. As of December 31, 2020, no amount of cash- settled RSUs have vested or been paid. 

## Stock Options 

Stock option activity is summarized as follows: 

<img src='content_image/1041413.jpg'>

All outstanding stock options at December 31, 2020 have vested. Stock options vest over a one to three-year service period, beginning at the date of grant, and the compensation cost is recognized ratably during the vesting period. Compensation cost for stock options subject to accelerated vesting at the date of retirement eligibility is recognized over the implicit service period. At December 31, 2020, we had no unrecognized compensation cost related to stock options. 

The intrinsic value of options exercised in 2020, 2019, and 2018 was $0.1 million, $0.3 million, and $0.7 million, respectively. There were no stock options granted or vested in the years 2018 through 2020. 

