In May 2019, our stockholders approved an amendment to our 2018 Incentive Plan (the “2018 Amended Plan”). An aggregate of 1.4 million shares of common stock were reserved for issuance to participants under the 2018 Amended Plan. The 2018 Amended Plan provides for the grant of long-term incentive awards to employees in various forms, including equity-based awards, time-vested cash awards and performance cash awards. Examples of stock-based awards that may be granted under the 2018 Amended Plan include nonqualified options, incentive stock options, share appreciation rights, restricted shares, restricted

share units, performance shares and performance units, dividend equivalents and other share-based awards. No new awards have been made under predecessor plans since the adoption of the 2018 Amended Plan.

In June 2020, our stockholders approved an additional amendment to the 2018 Amended Plan, which provided that an aggregate of 2.4 million shares of common stock were reserved for issuance to participants under the 2018 Amended Plan. The 2018 Amended Plan is administered by the compensation committee of our board of directors and as the administrator, the compensation committee, among other things, establishes the terms and conditions of awards granted under the 2018 Amended Plan. Awards outstanding under the 2018 Amended Plan will continue to be governed by the terms of such plan and agreements under which they were granted. The term of awards granted under the 2018 Amended Plan is limited to ten years, and no awards may be granted under the 2018 Amended Plan more than ten years after the effective date of such plan.

As of December 31, 2022, the 2018 Amended Plan had a total of 1.0 million shares of common stock available for future award grants to management and members of the board of directors. Our compensation expense for all plans was $13.5 million in 2022, $13.8 million in 2021 and $21.4 million in 2020. Income tax expense for share-based compensation was $3.3 million in 2022, $0.8 million in 2021 and $7.4 million in 2020.

Restricted stock units, which have been granted in units, and time-based cash awards generally vest and are expensed over one- or three- year periods. As of December 31, 2022, a total of 4.8 million restricted stock units have been granted under the 2018 Amended Plan and predecessor plans. All shares were valued at their fair market value, which is the closing price of the Company's stock on the date of grant. Unrecognized stock compensation cost as of December 31, 2022 is $13.7 million and will be recognized over the remaining weighted average life of 1.9 years.

In 2022, 2021 and 2020, we granted time-based cash awards to employees and recognized compensation expense totaling $4.4 million in 2022, $5.8 million in 2021 and $3.9 million in 2020. For the time-based cash awards, we had accruals of $3.3 million as of December 31, 2022 and $4.9 million as of December 31, 2021 in Accrued liabilities.

A summary of our restricted stock units as of December 31, 2022 and changes during the year then ended are presented below:


				Weighted-Average
Restricted Share Unit Awards	Number of Shares			Grant-Date Fair Value
Unvested as of December 31, 2021		363,249		$	43.79
Granted		223,075			72.65
Vested		(188,227	)		44.07
Forfeited		(7,365	)		48.18
Unvested as of December 31, 2022		390,732		$	60.00

The total fair value of shares vested on various vesting dates was $8.3 million in 2022, $10.3 million in 2021 and $15.7 million in 2020. Weighted average grant date fair value per share was $72.65 in 2022, $61.89 in 2021 and $27.74 in 2020.

Performance share unit awards and performance-based cash awards are expensed over three years, which generally is the requisite performance period. Awards generally vest if (1) we achieve certain specified performance levels as compared to predetermined performance thresholds during a three-year period starting on January 1 of the grant year and ending on December 31 three years later, and (2) except in the event of death, disability, or an involuntary termination without cause, the employee remains employed by us through the determination date, which can be no later than four months following the end of the Performance Period. Payment with respect to a performance share unit award or performance-based cash award may be prorated in connection with certain employee terminations. Performance share unit and performance-based cash awards include a relative total shareholder return (“TSR”) modifier which may impact the number of shares or cash earned at the end of the performance period. For these awards, the number of shares or cash earned based on the achievement of the predefined performance criteria will be reduced or increased if the Company's TSR over the performance period relative to a predefined comparator group of companies falls within defined ranges. The fair value of performance share units that include the TSR modifier is determined using a Monte Carlo valuation model on the date of grant, which requires inputs such as our common stock price, estimated common stock price volatility, and risk-free interest rate, among others.

The estimated compensation expense recognized for performance share unit and performance-based cash awards is net of estimated forfeitures. We assess the performance levels quarterly and record any change to compensation cost. We assess the TSR component for performance-based cash awards each quarter and record any change to compensation cost.

As of December 31, 2022, a total of 2.5 million performance share units have been granted. Unrecognized compensation cost as of December 31, 2022 is $4.2 million and will be recognized over the remaining weighted average life of 2.1 years. For the performance-based cash awards, we had accruals of $36.7 million as of December 31, 2022 and $39.7 million as of December 31, 2021. We recognized compensation expense associated with the performance-based cash awards totaling $19.5 million in 2022, $21.5 million in 2021 and $18.9 million in 2020.

A summary of our performance share units as of December 31, 2022 and changes during the year then ended are presented below:


				Weighted-Average
Performance Share Unit Awards	Number of Shares			Grant-Date Fair Value
Unvested as of December 31, 2021		229,538		$	53.31
Granted		72,091			78.46
Adjustments		135,405			-
Vested		(234,895	)		47.95
Forfeited		(769	)		56.92
Unvested as of December 31, 2022		201,370		$	64.93