The 2020 Plan and the 2013 Plan both provide for the granting of stock options, restricted stock, restricted stock units, stock appreciation rights, performance awards, other stock–based awards and dividend equivalent rights to our employees, directors and consultants. No additional grants may be made under the 2013 Plan following the adoption of the 2020 Plan. Previous grants made under the 2013 Plan continue to be governed by that plan and the applicable award agreements.

As of December 31, 2022, the maximum number of shares of common stock available for issuance under the 2020 Plan is 8,500,000, and 5.9 million shares remain available for grant. Each stock–settled award granted under the 2020 Plan reduces the number of shares available for issuance by one share. Cash–settled awards are not counted against the aggregate share limit. Shares subject to awards granted under the 2020 Plan that are subsequently canceled, terminated, settled in cash or forfeited, excluding shares withheld to satisfy tax withholding obligations or to pay the exercise price of an option, are available for future grant under the 2020 Plan. Our policy is to issue new shares when restricted stock units and performance–based restricted stock units are vested. We account for forfeitures as they occur.

Both the 2020 Plan and the 2013 Plan allow us to withhold shares upon vesting of restricted stock at the then–current market price to cover taxes required to be withheld on the vesting date. During the years ended December 31, 2022, 2021 and 2020, we withheld 283,024 shares valued at $2.4 million, 283,972 shares valued at $2.5 million and 236,752 shares valued at $1.8 million, respectively, to cover tax withholding.

Grants of restricted stock are subject to forfeiture, restrictions on transfer and certain other conditions until vesting, which generally occurs in three equal installments following the date of grant. Compensation expense is recognized over the vesting period equal to the fair value of our common stock at the grant date. Our restricted stock includes rights to receive dividends or dividend equivalents.

Grants of performance–based restricted stock units are three–year equity settled awards linked to the performance of our common stock. The awards also include dividend equivalent rights that accumulate during the vesting period.

The vesting of the performance–based restricted stock units is dependent of the satisfaction of a combination of certain service–related conditions and our total shareholder return ranked against that of a predetermined peer group over a three–year performance period. The awards vest in their entirety on the date specified in the award agreement following the conclusion of the performance period. The final number of shares of common stock issuable upon vesting can range from 0% to 200% of the initial grant depending on the level of achievement as determined by the Compensation Committee of our Board of Directors.

The fair value of the performance–based restricted stock units, incorporating the market condition, is estimated on the grant date using a Monte Carlo simulation model. Expected volatilities for us and each peer company utilized in the model are estimated using a historical period consistent with the awards’ remaining performance period as of the grant date. The risk–free interest rate is based on the yield on U.S. Treasury Separate Trading of Registered Interest and Principal Securities for a term consistent with the remaining performance period. The dividend yield used is 0.0% to approximate accumulation of earnings.

The assumptions that were used to estimate the fair value of our performance–based stock units are as follows:

Activity related to our restricted stock and performance–based restricted stock units is as follows:

The grant date fair value of the restricted stock and performance–based restricted stock units granted during the years ended December 31, 2022, 2021 and 2020 was $14.3 million, $12.1 million and $11.9 million, respectively. The fair value of the restricted stock and performance–based restricted stock units vested during the years ended December 31, 2022, 2021 and 2020 was $9.3 million, $8.5 million and $6.6 million, respectively.

As of December 31, 2022, we expect $12.7 million of unrecognized compensation cost related to our non–vested restricted stock and performance–based restricted stock units to be recognized over the weighted–average period of 1.8 years.

Grants of cash–settled performance units vest at the end of the three year vesting period and are payable in an amount of cash equivalent to the value of our common stock at the vesting date for each unit vested. These awards are subject to one of more performance conditions and are accounted for as liability awards with expense based on the fair value measured at the end of each reporting period. These awards also include dividend equivalent rights that accumulated during the vesting period. At the end of each reporting period, the Compensation Committee of our Board of Directors approves the determination of achievement for each performance measure, which can range from 0% to 200%.

The grant date fair value of the cash settled performance units granted during the years ended December 31, 2022, 2021 and 2020 was $2.5 million, $2.3 million and $1.8 million, respectively. Cash paid upon vesting of these cash settled performance units during the years ended December 31, 2022, 2021 and 2020 was $1.2 million, $0.6 million and $0.5 million, respectively.

As of December 31, 2022, we expect $3.0 million of unrecognized compensation cost related to our non–vested liability awards to be recognized over the weighted–average period of 1.9 years.

Our ESPP provides employees with an opportunity to participate in our long–term performance and success through the purchase of shares of common stock at a price that may be less than fair market value. Each quarter, eligible employees may elect to withhold a portion of their salary up to the lesser of $25,000 per year or 10% of their eligible pay at a price equal to 85% to 100% of the fair market value of the stock as defined by the plan. The purchase discount under the ESPP is 5% of the fair market value of our common stock on the first or last trading day of the quarter, whichever is lesser. Our ESPP is compensatory and, as a result, we record an expense in our consolidated statements of operations related to the ESPP.

The ESPP will terminate on the date that all shares of common stock authorized for sale under the ESPP have been purchased, unless it is extended. The maximum number of shares of common stock available for purchase under the ESPP is 1.0 million. As of December 31, 2022, 429,250 shares remained available for purchase under the ESPP.

Our DSDP provides non–employee members of the Board of Directors with an opportunity to elect to receive our common stock as payment for a portion or all of their retainer. The number of shares paid each quarter is determined by dividing the dollar amount of fees elected to be paid in common stock by the closing sales price per share of the common stock on the last day of the quarter. In addition, directors who elect to receive a portion or all of their fees in the form of common stock may also elect to defer, until a later date, the receipt of a portion or all of their fees to be received in common stock. In this case, we issue restricted stock units and the rights to receive dividends or dividend equivalents is accrued and paid when the shares are issued.

There are 100,000 shares reserved under the DSDP and, as of December 31, 2022, 37,771 shares remained available to be issued under the plan.

(1)	In 2021, we reversed a prior period expense of $2.1 million as the result of revised estimates of performance achievement of our 2020 and 2019 cash–settled performance–based restricted stock units.