The Company has several incentive plans under which stock options, restricted stock units (RSUs), restricted stock awards (RSAs), and cash-settled stock appreciation rights (SARs) have been issued, including the Third Amended and Restated 2006 Omnibus Long-Term Incentive Plan, as amended, and a plan and private placement issuances related to the Company’s acquisition of Machinio. As of September 30, 2021, the Company has reserved at total of 19,100,000 shares of its common stock for exercises of stock options, vesting of RSUs, and grants of RSAs under these plans. Vesting of RSUs and grants of RSAs count as 1.5x shares against the plan reserves. As of September 30, 2021, 1,993,244 shares of common stock remained available for use.

The table below presents the components of share-based compensation expense (in thousands):


	Year Ended September 30,
	2021		2020		2019
Equity-classified awards:
Stock options	$	3,117	$	2,054	$	1,530
RSUs & RSAs	2,977		3,635		4,496
Liability-classified awards:
SARs	$	853	$	(29)	$	482
Total stock compensation expense:	$	6,947	$	5,660	$	6,508

The Company’s total liabilities for liability-classified stock compensation awards was $0.5 million and $0.1 million as of September 30, 2021 and 2020, the current portion of which was $0.3 million and $0.1 million, respectively.


	Stock Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding as of September 30, 2020	3,075,914	$	8.54	6.16	$	2,841
Granted	1,108,273	$	10.60		$	—
Exercised	(1,033,529)	$	6.59		$	15,036
Forfeited	(272,720)	$	7.82		$	2,547
Expired	(33,653)	$	15.35		$	108
Outstanding as of September 30, 2021	2,844,285	$	10.04	6.14	$	34,877
Vested and expected to vest as of September 30, 2021	2,810,202	$	9.94	6.10	$	34,775
Exercisable as of September 30, 2021	1,477,408	$	10.37	4.24	$	18,589

Of the 1,366,877 stock options not yet exercisable as of September 30, 2021, 853,553 can become exercisable by satisfying service conditions only, and 513,324 can become exercisable by satisfying service and performance or market conditions.

Stock options containing only service conditions generally vest over periods of one to four years and expire five to ten years from the date of grant. Stock compensation cost is expensed ratably over the entire service period. As of September 30, 2021, there was $2.7 million of unrecognized compensation cost related to stock options containing only service conditions, which is expected to be recognized over a weighted-average period of 2.8 years.


	Year ended September 30
	2021	2020	2019
Dividend yield	—	—	—
Expected volatility	51.0% - 55.9%	46.5% - 51.0%	47.8% - 53.7%
Risk-free interest rate	0.4% - 0.8%	0.5% - 1.5%	1.9% - 2.8%
Expected term	4.6- 7.6 years	4.6 - 7.4 years	4.2 - 7.1 years

The weighted-average grant date fair value of options granted during the year-ended September 30, 2021, 2020 and 2019 was $4.81, $2.66 and $2.70, respectively. The total intrinsic value of options exercised during 2021, 2020 and 2019 was $15.0 million, $0.1 million and $0.3 million, respectively. Stock options containing performance conditions are discussed separately in the section below.


	RSU & RSA	Weighted- Average Grant Date Fair Value		Weighted- Average Remaining Contractual Term (years)	Aggregate Fair Value
Outstanding as of September 30, 2020	1,545,285	$	6.84	1.85	$	11,528
Granted	330,545	$	14.08		$	4,653
Vested	(811,773)	$	6.78		$	13,780
Forfeited	(146,676)	$	8.98		$	2,688
Outstanding as of September 30, 2021	917,381	$	9.15	1.98	$	19,825
Expected to vest as of September 30, 2021	666,092	$	10.17	2.35	$	14,394

RSUs containing only service conditions vest ratably each year over periods of one to four years. Stock compensation cost is expensed ratably over the entire service period. As of September 30, 2021, there was $3.6 million of unrecognized compensation cost related to RSUs containing only service conditions, which is expected to be recognized over a weighted-average period of 2.9 years. RSUs and RSAs containing performance conditions and market conditions are discussed separately in the section below.


	SARs	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)	Aggregate Intrinsic Value
Outstanding as of September 30, 2020	160,810	$	8.45	1.00	$	96

Exercised	(45,084)	$	8.45		$	443
Forfeited	(73,681)	$	9.80		$	213
Outstanding as of September 30, 2021	42,045	$	6.11	1.26	$	652
Vested and expected to vest as of September 30, 2021	42,045	$	6.11	1.26	$	652
Exercisable as of September 30, 2021	12,045	$	6.11	1.26	$	187

As of September 30, 2021, there was $0.3 million of unrecognized compensation cost related to SARs containing service conditions, which is expected to be recognized over a weighted-average period of 1.3 years. The Company made cash payments of $0.4 million, $0.6 million and $0.5 million to settle SARs exercised during the years ended September 30, 2021, 2020 and 2019, respectively.

The fair value of outstanding SARs containing only service conditions is estimated using the Black-Scholes option-pricing model. The range of assumptions used to determine the fair value of outstanding SARs as of September 30, 2021, 2020 and 2019 were as follows:


	Year ended September 30
	2021	2020	2019
Dividend yield	—	—	—
Expected volatility	78.3% - 78.3%	55.0% - 68.8%	38.2% - 48.8%
Risk-free interest rate	0.1% - 0.1%	0.1% - 0.1%	1.3% - 1.7%
Expected term	1.3-1.3 years	0.0-2.3 years	0.1-3.3 years

As of September 30, 2021 and 2020, the weighted-average fair value of SARs outstanding was $18.86 and $0.63 per award, respectively. SARs containing performance conditions and market conditions are discussed separately in the section below.

Stock awards containing performance conditions vest upon the achievement of specified financial targets of the Company or its business units. Vesting is generally measured on the first day of each fiscal quarter over the four-year terms of the awards, starting with the first fiscal quarter after the first anniversary of the grant date, based upon the trailing twelve months performance of the Company or its business units. When it is probable that the performance targets will be achieved, stock compensation expense is recognized ratably over the derived service period. If the Company determines that achievement of the performance targets is no longer probable, the Company no longer records expense and reverses all previously recognized expense. As of September 30, 2021, there was $0.4 million of unrecognized compensation costs related to stock options and RSUs & RSAs, containing performance conditions that are considered probable of being met, which is expected to be recognized over a weighted-average period of 3.0 years.

Stock awards containing market conditions vest upon the achievement of specified increases in the Company’s share price. Vesting is measured the first day of each fiscal quarter over the four-year terms of the award, starting with the first fiscal quarter after the first anniversary of the grant date, based upon the trailing 20-days average of the Company’s share price. Stock compensation cost is expensed on a straight-line basis over the derived service period for each stock price target within the award. The Company accelerates expense when a stock price target is achieved prior to the derived service period. For equity-classified awards, the Company does not reverse expense recognized if the stock price target(s) are not ultimately achieved, but expense is reversed when such situations occur for liability classified awards. As of September 30, 2021, there was $0.9 million of unrecognized compensation costs related to stock options, RSUs and SARs, containing market conditions, which is expected to be recognized over a weighted-average period of 0.5 years.

The fair value of stock options, RSUs and SARs containing market conditions is estimated using Monte Carlo simulations. The range of assumptions used to determine the fair value of these awards during the years ended September 30, 2021, 2020 and 2019 were as follows:


	Year ended September 30
	2021	2020	2019
Dividend yield	—	—	—
Expected volatility	51.6% - 54.6%	45.2% - 54.9%	45.5% - 55.0%
Risk-free interest rate	0.3% - 0.9%	0.1% - 1.7%	1.5% - 2.9%
Expected holding period (% of remaining term)	31.7% - 100.0%	30.7% - 100.0%	25.9% - 100.0%

We are authorized to repurchase issued and outstanding shares of our common stock under a share repurchase program approved by our Board of Directors. Share repurchases may be made through open market purchases, privately negotiated transactions or otherwise, at times and in such amounts as management deems appropriate. The timing and actual number of shares repurchased will depend on a variety of factors including price, corporate and regulatory requirements and other market conditions. The repurchase program may be discontinued or suspended at any time and will be funded using our available cash.

As of the fiscal year ended September 30, 2020, we had $6.1 million of remaining share repurchase authorization. On March 8, 2021, our Board of Directors authorized an additional $10 million of share repurchases of the Company's outstanding shares of common stock through March 31, 2023. We repurchased 957,079 shares for $16.1 million under this program during the six months ended March 31, 2021.

On May 3, 2021, the Company's Board of Directors authorized a new stock repurchase plan (the “May 3, 2021 Stock Repurchase Plan”) of up to $15 million of our outstanding shares of common stock through June 30, 2023. We repurchased 634,884 shares for $15.0 million under this program during the year ended September 30, 2021. On December 6, 2021, the Company's Board of Directors authorized the repurchase of up to $20 million of the Company's outstanding shares of common stock through December 31, 2023.

Separate from the share repurchase program, our stock incentive plans allow for participants to exercise stock options by surrendering shares of common stock equivalent in value to the exercise price due. During the three months ended June 30, 2021, no shares of common stock were surrendered by participants in the exercise of stock options. During the year ended September 30, 2021, participants surrendered 82,612 shares of common stock in the exercise of stock options. Any shares surrendered to the Company in this manner are not available for future grant.