For a detailed explanation of the Company’s stock plans, refer to Note 14, Employee Benefits and Share-Based Compensation, of the audited Consolidated Financial Statements and accompanying Notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on February 25, 2022.

The following table sets forth the total share-based compensation expense recognized in the Company’s Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2022 and 2021:


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021

	(In thousands)
Cost of product and service revenues	$	2,160	$	2,044	$	4,404	$	3,981
Research and development	2,594		1,731		4,858		3,431
Selling, general, and administrative	12,459		9,264		24,159		17,399
Total share-based compensation expense	$	17,213	$	13,039	$	33,421	$	24,811


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Expected life, years	0.5 - 2.0		0.5 - 2.0		0.5 - 2.0		0.5 - 2.0
Expected volatility, %	28.8% - 45.6%		27.4% - 53.5%		28.8% - 45.6%		27.4% - 53.5%
Risk-free interest rate, %	0.1% - 1.5%		0.1% - 2.6%		0.1% - 1.5%		0.1% - 2.6%
Dividend yield, %	—	%	—	%	—	%	—	%

For the six months ended June 30, 2022 and 2021, employees purchased approximately 175,000 and 156,000 shares of common stock, respectively, under the ESPP at a weighted-average price of $66.81 and $59.75, respectively. As of June 30, 2022, the unrecognized compensation cost related to the shares to be purchased under the ESPP was approximately $2.5 million and is expected to be recognized over a weighted-average period of 1.2 years.

The following assumptions were used to value stock options granted pursuant to the Company’s 2009 Equity Incentive Plan, as amended, (the “2009 Plan”) for the six months ended June 30, 2021. There were no stock options granted during the three and six months ended June 30, 2022, and the three months ended June 30, 2021.


	Six Months Ended June 30,
		2021
Expected life, years		4.9
Expected volatility, %		30.1	%
Risk-free interest rate, %		0.6	%
Estimated forfeiture rate, %		7.9	%
Dividend yield, %		—	%


	Number of Shares	Weighted-Average Exercise Price		Weighted-Average Remaining Years	Aggregate Intrinsic Value

	(In thousands, except per share data)
Outstanding at December 31, 2021	2,954	$	67.35	6.9	$	334,119
Granted	—	—
Exercised	(184)	51.25
Expired	(4)	73.01
Forfeited	(69)	85.82
Outstanding at June 30, 2022	2,697	$	67.96	6.5	$	125,696
Exercisable at June 30, 2022	1,813	$	60.51	5.9	$	97,069
Vested and expected to vest at June 30, 2022 and thereafter	2,625	$	67.46	6.4	$	123,496

The weighted-average fair value per share of options granted during the six months ended June 30, 2021 was $33.89. The intrinsic value of options exercised during the three months ended June 30, 2022 and 2021 was $2.8 million and $16.8 million, respectively, and during the six months ended June 30, 2022 and 2021 was $15.5 million and $30.8 million, respectively.

As of June 30, 2022, total unrecognized compensation cost related to unvested stock options was $24.2 million, which is expected to be recognized over a weighted-average vesting period of 1.8 years.


	Number of Shares	Weighted-Average Grant Date Fair Value		Weighted-Average Remaining Years	Aggregate Intrinsic Value

	(In thousands, except per share data)

Outstanding at December 31, 2021	763	$	119.93	1.6	$	137,696
Granted (Awarded)	571	119.58
Vested (Released)	(111)	96.01
Forfeited	(53)	125.46
Outstanding and unvested at June 30, 2022	1,170	$	121.78	1.7	$	133,143

As of June 30, 2022, total unrecognized compensation cost related to RSUs was $113.6 million, which is expected to be recognized over the remaining weighted-average vesting period of 3.3 years.


	Number of Shares	Weighted-Average Grant Date Fair Value

	(In thousands, except per share data)

Outstanding at December 31, 2021	11	$	137.36
Granted (Awarded)	13	109.39
Vested (Released)	(11)	137.36

Outstanding and unvested at June 30, 2022	13	$	109.39

As of June 30, 2022, total unrecognized compensation cost related to RSAs was $1.1 million, which is expected to be recognized over the remaining weighted-average vesting period of 0.9 years.


	Number of Shares	Weighted-Average Grant Date Fair Value Per Unit

	(In thousands, except per share data)
Outstanding at December 31, 2021	144	$	118.71
Granted	78	155.27
Additional granted based on performance achievement	51	156.79
Vested	(84)	117.37
Forfeited	(1)	178.81
Outstanding and unvested at June 30, 2022	188	$	144.76

As of June 30, 2022, total unrecognized compensation cost related to PSUs was approximately $11.4 million, which is expected to be recognized over the remaining weighted-average vesting period of 1.4 years.


			Number of Shares

			(In thousands)
Share options outstanding			2,697
Non-vested restricted stock awards			1,371
Shares authorized for future issuance			1,467
ESPP shares available for future issuance			744
Total shares reserved for future issuance			6,279

On August 2, 2016, the Company’s Board of Directors (the “Board”) authorized a stock repurchase program providing for the repurchase of up to $50.0 million of the Company’s common stock (the “2016 Repurchase Program”). The 2016 Repurchase Program is in addition to the stock repurchase program approved by the Board on November 4, 2014 providing for the repurchase of up to $50.0 million of the Company’s common stock (the “2014 Repurchase Program”). During the first quarter of 2022, the 2014 Repurchase Program was completed, and as of June 30, 2022, the maximum dollar value of shares that may yet be purchased under the 2016 Repurchase Program was $2.7 million. The 2016 Repurchase Program does not obligate the Company to repurchase any specific number of shares, and the Company may terminate or suspend the 2016 Repurchase Program at any time.