The Company's 2020 Stock Incentive Plan (the "2020 Plan"), which provides for share-based awards to Company employees, non-employee directors and outside consultants or advisors, was approved by stockholders on May 27, 2020. The 2020 Plan replaced the Company’s 2015 Stock Incentive Plan (the “2015 Plan”), and no new share-based awards may be granted under the 2015 Plan. On June 5, 2023, the Company's stockholders approved an increase in the number of shares of common stock reserved for issuance under the 2020 Plan from 375,000 to 725,000. The number of shares available for grants of awards at December 31, 2023 was 312,398.

Share-based compensation expense included in selling, general and administrative expenses during the years ended December 31, 2023, 2022 and 2021, was $8.5 million, $7.4 million and $5.4 million, respectively. Related income tax benefits for the years ended December 31, 2023, 2022 and 2021, were $1.6 million, $1.2 million and $1.3 million, respectively.

Outstanding stock options generally vest over either four or eight years and expire ten years after the date of grant.

A summary of the status of the Company’s stock options at December 31, 2023, together with changes during the periods then ended, is presented below:


						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Number			Exercise		Contractual		Value
	of Options			Price		Term (Years)		(In Thousands)
Outstanding at December 31, 2022		101,125		$	70.81		—		—
Options exercised		(1,125	)		2.05		—		—
Outstanding at December 31, 2023		100,000			71.59		3.65		4,421
Exercisable at December 31, 2023		40,000		$	55.65		2.78	$	2,406

No stock options were granted during the years ended December 31, 2023, 2022 and 2021.

The intrinsic value of stock options exercised for the years ended December 31, 2023, 2022 and 2021 was $0.1 million, $0.2 million, and $1.7 million, respectively. The fair value of stock options vested for the year ended December 31, 2022 was $728,000. No stock options vested during the year ended December 31, 2023 or 2021. As of December 31, 2023, unrecognized compensation expense related to stock options was $1.5 million with a weighted average remaining amortization period of 2.2 years.

Restricted stock units generally vest in four equal annual installments beginning one year following the date of grant.

The following table presents restricted stock unit activity:


				Weighted Average
				Grant Date
	Units			Fair Value
Nonvested at December 31, 2022		210,982		$	68.33
Granted		89,934			87.94
Vested		(76,127	)		67.60
Cancelled/Forfeited		(5,511	)		70.37
Nonvested at December 31, 2023		219,278		$	76.57

The total fair value of restricted stock units vested during the years ended December 31, 2023, 2022 and 2021 was $5.1 million, $4.5 million and $3.6 million, respectively. As of December 31, 2023, unrecognized compensation expense related to restricted stock units was $12.7 million with a weighted average remaining amortization period of 2.7 years.

Performance share units (“PSUs”) are granted to key employees of the Company and are conditioned on attaining financial performance metrics specified in each award. Each award is subject to upward or downward adjustment depending on whether achievement of the financial metrics is above or below the target level, with a maximum payout of up to 200% of the target number of shares covered by the award.

PSUs vest on the date that the Compensation Committee determines the level of attainment of the specified financial metrics, generally measured over a three-year period.

The following table presents PSU activity:


				Weighted Average
				Grant Date
	Units			Fair Value
Nonvested at December 31, 2022		53,968		$	65.13
Granted		30,695			83.77
Vested		(23,369	)		69.17
Nonvested at December 31, 2023		61,294		$	72.93

The total grant date fair value of PSUs vested during the years ended December 31, 2023, 2022 and 2021 was $1.6 million, $259,000, and $276,000, respectively.

The Company offers employees the right to purchase shares at a discount from the market price under the Company’s 2019 Employee Stock Purchase Plan. Subject to the annual statutory limit, employees are eligible to participate through payroll deductions of up to 15% of their compensation. At the end of each six-month offering period, shares are purchased by the participants at 85% of the fair market value at the end of the offering period. As of December 31, 2023, approximately 264,000 shares were reserved for future issuance under the 2019 Employee Stock Purchase Plan.