15.    STOCK-BASED COMPENSATION

Stock Compensation Plans

Time Lapse Restricted Shares and Restricted Stock Units

Time lapse restricted shares (TLRSs) have been issued to officers and other employees under the Company’s Employee Stock Incentive Plan. The Company recognizes compensation expense for the unvested portion of awards outstanding over the remainder of the service period. The compensation cost recorded for these awards is based on their closing stock price at the grant date less the cost of estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods to reflect actual forfeitures.

TLRSs provide for the issuance of a share of the Company’s common stock at no cost to the holder and generally vest after a certain stipulated number of years from the grant date, depending on the terms of the issue. TLRSs vest in 20 percent increments starting with the second anniversary of the grant, over six years from the date of grant. During these years, grantees receive all dividends declared and retain voting rights for the granted shares. The agreements under which the one-time grant of restricted stock is issued provide that shares awarded may not be sold or otherwise transferred until restrictions established under the plans have lapsed.

The Company issued time lapse restricted shares of 0.8 million, 0.9 million, and 0.7 million for the years ended December 31, 2021, 2020, and 2019, respectively.

The Company issues new shares from its authorized but unissued share pool. At December 31, 2021, approximately 6.6 million shares of the Company’s common stock were reserved for issuance. In accordance with the FASB ASC Topic 718, “Compensation – Stock

Compensation,” the Company recognizes the fair value of the award on a straight-line basis over the service periods of each award. The Company estimates restricted share employee forfeiture rates based on its historical experience.

The following table summarizes the components of the Company’s stock-based compensation programs recorded as expense ($ in thousands):

​

​

As of December 31, 2021 and 2020, $49.8 million and $40.5 million, respectively, of total unrecognized compensation cost related to time-lapse restricted shares are expected to be recognized over a weighted average period of approximately 4.0 years and 3.8 years at December 31, 2021 and 2020, respectively.

The following table summarizes information on unvested restricted stock units outstanding as of December 31, 2021, 2020 and 2019.

​

​