The 2019 Stock Omnibus Incentive Plan (the “2019 Plan”), which expires in 2029, permits the grant of various forms of stock-based awards. The terms and vesting schedules for the stock-based awards vary by type and date of grant. A maximum of 3.1 million stock options, restricted stock or other stock-based compensation awards may be granted. Shares subject to award under the 2019 Plan may be either authorized but unissued shares of our common stock or treasury shares. Refer to the Annual Report on Form 10-K for the year ended December 31, 2019 for further discussion on the 2019 Plan.

Compensation expense for stock-based awards recognized during the three and six months ended June 30, 2020 and 2019 was as follows (in thousands):

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2020		2019		2020		2019
Stock options	$	367	$	479	$	788	$	998
Restricted stock units and awards		1,324		1,153		2,495		2,082
Performance share units		566		285		997		319
Total stock-based compensation expense	$	2,257	$	1,917	$	4,280	$	3,399

Stock Options and Restricted Stock Units and Awards – The following table presents our stock options and restricted stock award activity during the six months ended June 30, 2020 (in thousands, except per share data):

	Stock Options					Restricted Stock Units and Awards
	Number of Options			Weighted Average Exercise Price Per Share		Number of Shares			Weighted Average Grant-Date Fair Value (1)
Outstanding at beginning of year		2,412		$	13.58		577		$	17.87
Granted		—		$	—		178		$	24.48
Exercised or released		(327	)	$	9.88		(276	)	$	16.74
Expired or canceled		(8	)	$	18.15		(9	)	$	20.96
Outstanding at June 30, 2020		2,077		$	14.14		470		$	20.97
Exercisable at June 30, 2020		1,605		$	12.96

Performance Share Units (“PSUs”) – PSUs are earned based on our financial performance over a contractual term of three years and the associated expense is recognized over that period based on the fair value of the award. A three-year cliff vesting schedule of the PSUs is dependent upon the Company’s performance relative to pre-established goals based on achievement of an earnings per share target (weighted 70%) and achievement of total growth in revenue (weighted 30%). The fair value of PSUs is calculated using the market value of a share of our common stock on the date of grant. For performance achieved above specified levels, the recipient may earn additional shares of stock, not to exceed 200% of the number of PSUs initially granted.

The following table presents our PSU award activity during the six months ended June 30, 2020 (in thousands, except per share data):

	Performance Share Units			Weighted Average Grant-Date Fair Value Per Unit
Outstanding at beginning of year		200		$	19.82
Granted		132		$	25.75
Vested		—		$	—
Adjustments for performance results		—		$	—
Expired or canceled		(8	)	$	22.14
Outstanding at June 30, 2020		324		$	22.17