We grant share-based compensation awards to our officers, directors, and certain key employees pursuant to the 2017 Viad Corp Omnibus Incentive Plan (the “2017 Plan”). The 2017 Plan has a 10-year term and provides for the following types of awards: (a) incentive and non-qualified stock options; (b) restricted stock awards and restricted stock units; (c) performance units or performance shares; (d) stock appreciation rights; (e) cash-based awards; and (f) certain other stock-based awards. In June 2017, we registered 1,750,000 shares of common stock issuable under the 2017 Plan. As of March 31, 2021, there were 759,578 shares available for future grant under the 2017 Plan.

	Three Months Ended
	March 31,
(in thousands)	2021			2020
Performance-based restricted stock units	$	140		$	(2,635	)
Restricted stock awards and restricted stock units		1,244			490
Stock options		379			—
Share-based compensation (income) expense before income tax		1,763			(2,145	)
Income tax benefit⁽¹⁾		(27	)		(109	)
Share-based compensation (income) expense, net of income tax	$	1,736		$	(2,254	)

Performance-based restricted stock units (“PRSU”) are tied to our stock price and the expected achievement of certain performance-based criteria. The vesting of PRSU shares is based upon the achievement of the performance-based criteria over a three to four-year period. We account for PRSU awards that will be settled in shares of our common stock as equity-based awards. We measure share-based compensation expense of equity-based awards at fair value on the grant date on a straight-line basis over the vesting period. The estimated number of shares to be achieved is updated each reporting period. We account for PRSU awards that will be settled in cash as liability-based awards. We measure share-based compensation expense of liability-based awards at fair value at each reporting date until the date of settlement. Forfeitures are accounted for as they occur.

During the three months ended March 31, 2021, we granted PRSU awards with a grant date fair value of $3.2 million, all of which are payable in shares.

In 2021, PRSU awards granted in 2018 vested; however, as performance metrics were not achieved, no awards were paid in cash or in shares. In 2020, PRSU awards granted in 2017 vested and we paid $2.6 million in cash. No PRSU awards were paid in shares in 2020.

As of March 31, 2021, the unamortized cost of outstanding equity-based PRSU awards was $3.1 million, which we expect to recognize over a weighted-average period of approximately 2.8 years. Liabilities related to liability-based PRSU awards were $0.9 million as of March 31, 2021 and $0.8 million as of December 31, 2020.

	Equity-Based PRSU Awards				Liability-Based PRSU Awards
	Shares		Weighted-Average Grant Date Fair Value		Shares			Weighted-Average Grant Date Fair Value
Balance at December 31, 2020		61,208	$	57.18		121,485		$	56.34
Granted		101,785	$	31.28		—		$	—
Vested		—	$	—		(42,698	)	$	51.96
Forfeited		—	$	—		(703	)	$	56.97
Balance at March 31, 2021		162,993	$	41.01		78,084		$	57.12

Restricted stock awards and restricted stock units are service-based awards. We account for restricted stock awards and restricted stock units that will be settled in shares of our common stock as equity-based awards. We measure share-based compensation expense of equity-based awards at fair value on the grant date on a straight-line basis over the vesting period.

We account for restricted stock units that will be settled in cash as liability-based awards. We measure share-based compensation expense of liability-based awards at fair value at each reporting date until the date of settlement. Forfeitures are recorded when they occur.

As of March 31, 2021, the unamortized cost of outstanding equity-based restricted stock awards and restricted stock units was $6.8 million, which we expect to recognize over a weighted-average period of approximately 1.3 years. We repurchased 12,055 shares for $0.5 million during the three months ended March 31, 2021 and 17,674 shares for $1.1 million during the three months ended March 31, 2020 related to tax withholding requirements on vested share-based awards.

Aggregate liabilities related to liability-based restricted stock units were $0.2 million as of March 31, 2021 and $0.2 million as of December 31, 2020. During the three months ended March 31, 2021, 3,174 restricted stock units vested, and we paid $0.1 million in cash. During the three months ended March 31, 2020, 2,815 restricted stock units vested, and we paid $0.2 million in cash.

The following table summarizes the activity of the outstanding restricted stock awards and restricted stock units:

	Equity-Based Restricted Stock Awards					Equity-Based Restricted Stock Units					Liability-Based Restricted Stock Units
	Shares			Weighted-Average Grant Date Fair Value		Shares			Weighted-Average Grant Date Fair Value		Shares			Weighted-Average Grant Date Fair Value
Balance at December 31, 2020		107,107		$	53.23		151,261		$	19.51		10,459		$	51.91
Granted		22,320		$	44.80		62,919		$	44.79		—		$	—
Vested		(37,170	)	$	53.86		—		$	—		(3,174	)	$	52.24
Forfeited		(1,030	)	$	56.94		(2,026	)	$	19.75		—		$	—
Balance at March 31, 2021		91,227		$	50.87		212,154		$	27.00		7,285		$	53.34

We grant non-qualified stock options that are performance-based, as well as non-qualified options that are service-based. The performance-based awards are recognized on a straight-line basis over the performance period ranging from 1.0 to 3.4 years, and the underlying shares expected to be settled are adjusted each reporting period based on estimated future achievement of the respective performance metrics. The service-based awards are recognized on a straight-line basis over the requisite service period on a graded-vesting schedule over two years.

	Shares		Weighted-Average Exercise Price		Aggregate Intrinsic Value⁽¹⁾
Options outstanding at December 31, 2020		204,150	$	19.98
Granted		137,858	$	44.80
Exercised		—	$	—
Options outstanding at March 31, 2021		342,008	$	29.98	$	4,445,085
Options exercisable at March 31, 2021		—	$	—	$	—

The following table summarizes stock options outstanding and exercisable as of March 31, 2021:

		Options Outstanding						Options Exercisable
Range of exercise prices		Shares		Weighted-Average Remaining Contractual Life (in years)		Weighted-Average Exercise Price		Shares		Weighted-Average Exercise Price
$	19.30		150,000		7.75	$	19.30		—	$	—
$	21.85		54,150		6.41	$	21.85		—	$	—
$	44.80		137,858		6.90	$	44.80		—	$	—
$19.30 - $44.80			342,008		7.20	$	29.98		—	$	—

The fair value of stock options granted in 2021 was estimated on the date of grant using the Black-Scholes option pricing model.

Following is additional information on stock options granted during the three months ended March 31, 2021 and the underlying assumptions used in assessing fair value:

	Three Months Ended
	March 31, 2021
Assumptions used to estimate fair value of stock options granted:
Risk-free interest rate	0.50%
Expected term (in years)		4.5
Expected volatility	55.8%
Expected dividend yield		—
Weighted average grant-date fair value per share of options granted	$	20.26

As of March 31, 2021, the total unrecognized compensation cost related to non-vested stock option awards was $3.8 million. We expect to recognize such costs over a weighted-average period of approximately 1.9 years.