The Company’s 2013 Stock Incentive Plan (as amended, the “2013 Equity Plan”) authorizes the issuance of various types of share-based awards to the Company’s employees, officers, directors, and other eligible participants. As of March 31, 2022, a total of 2,750,000 shares of the Company’s class A common stock were authorized for issuance under the 2013 Equity Plan. As of March 31, 2022, there were 241,334 shares of class A common stock reserved and available for future issuance under the 2013 Equity Plan.

As of March 31, 2022, there were options to purchase 1,465,779 shares of class A common stock outstanding under the 2013 Equity Plan.

The following table summarizes the Company’s stock option activity (in thousands, except per share data and years) for the three months ended March 31, 2022:

	Stock Options Outstanding
				Weighted Average		Aggregate		Weighted Average
				Exercise Price		Intrinsic		Remaining Contractual
	Shares			Per Share		Value		Term (Years)
Balance as of January 1, 2022		1,167		$	268.74
Granted		304		$	404.60
Exercised		(2	)	$	129.23	$	678
Forfeited/Expired		(3	)	$	445.94
Balance as of March 31, 2022		1,466		$	296.80
Exercisable as of March 31, 2022		698		$	184.99	$	223,826		4.0
Expected to vest as of March 31, 2022		768		$	398.27	$	108,378		8.9
Total		1,466		$	296.80	$	332,204		6.6

Stock options outstanding as of March 31, 2022 are comprised of the following range of exercise prices per share (in thousands, except per share data and years):

	Stock Options Outstanding at March 31, 2022
			Weighted Average		Weighted Average
			Exercise Price		Remaining Contractual
Range of Exercise Prices per Share	Shares		Per Share		Term (Years)
$121.43 - $200.00		876	$	135.94		4.7
$400.01 - $500.00		324	$	408.64		9.8
$600.01 - $691.23		266	$	691.23		8.9
Total		1,466	$	296.80		6.6

An aggregate of 123,625 stock options with an aggregate grant date fair value of $28.4 million vested during the three months ended March 31, 2022. The weighted average grant date fair value of stock option awards using the Black-Scholes valuation model was $227.51 and $381.26 for each share subject to a stock option granted during the three months ended March 31, 2022 and 2021, respectively, based on the following assumptions:

	Three months ended
	March 31,
	2022			2021
Expected term of options in years		6.3				6.3
Expected volatility		58.4	%		57.6% - 59.0%
Risk-free interest rate		1.9	%		0.8% - 1.0%
Expected dividend yield		0.0	%			0.0	%

For the three months ended March 31, 2022 and 2021, the Company recognized approximately $10.4 million and $5.3 million, respectively, in share-based compensation expense from stock options granted under the 2013 Equity Plan. As of March 31, 2022, there was approximately $154.2 million of total unrecognized share-based compensation expense related to unvested stock options. As of March 31, 2022, the Company expects to recognize this remaining share-based compensation expense over a weighted average vesting period of approximately 3.3 years.

As of March 31, 2022, there were 108,273 share-settled restricted stock units outstanding under the 2013 Equity Plan. The following table summarizes the Company’s share-settled restricted stock unit activity (in thousands) for the periods indicated:

	Share-Settled Restricted Stock Units Outstanding
				Aggregate
				Intrinsic
	Units			Value
Balance as of January 1, 2022		105
Granted		11
Vested		(4	)	$	1,433
Forfeited		(4	)
Balance as of March 31, 2022		108
Expected to vest as of March 31, 2022		108		$	52,655

During the three months ended March 31, 2022, 3,927 share-settled restricted stock units having an aggregate grant date fair value of $2.7 million vested, and 1,473 shares were withheld to satisfy tax obligations, resulting in 2,454 issued shares. The weighted average grant date fair value of share-settled restricted stock units granted during the three months ended March 31, 2022 and 2021 was $404.60 and $691.99, respectively, based on the fair value of the Company’s class A common stock. For the three months ended March 31, 2022 and 2021, the Company recognized approximately $3.2 million and $1.2 million, respectively, in share-based compensation expense from share-settled restricted stock units granted under the 2013 Equity Plan. As of March 31, 2022, there was approximately $44.1 million of total unrecognized share-based compensation expense related to unvested share-settled restricted stock units. As of March 31, 2022, the Company expects to recognize this remaining share-based compensation expense over a weighted average vesting period of approximately 3.2 years.

From time to time the Company has granted “other stock-based awards” and “cash-settled restricted stock units” under the 2013 Equity Plan. Other stock-based awards are similar to stock options, and cash-settled restricted stock units are similar to the Company’s share-settled restricted stock units, except in each case these awards are settled in cash only and not in shares of the Company’s class A common stock. Due to their required cash settlement feature, these awards are classified as liabilities in the Company’s Consolidated Balance Sheets and the fair value of the awards is remeasured each quarterly reporting period. For the three months ended March 31, 2022 and 2021, the Company recognized approximately $0.1 million and $0.9 million, respectively, in share-based compensation expense from other stock-based awards and cash-settled restricted stock units. As of March 31, 2022, there was approximately $2.0 million of total unrecognized share-based compensation expense related to other stock-based awards and cash-settled restricted stock units. As of March 31, 2022, the Company expects to recognize this remaining share-based compensation expense over a weighted average vesting period of approximately 2.8 years, subject to additional fair value adjustments through the earlier of settlement or expiration.

The Company also maintains the 2021 Employee Stock Purchase Plan (the “2021 ESPP”). The purpose of the 2021 ESPP is to provide eligible employees of the Company and certain of its subsidiaries with opportunities to purchase shares of the Company’s class A common stock, commencing at such time and on such dates as the Board of Directors of the Company shall determine. The first offering period under the 2021 ESPP commenced on February 16, 2021 and ended on August 15, 2021. After this first offering period, the Board of Directors of the Company determined to provide subsequent 6-month offering periods commencing on each March 1 and September 1 for the remaining term of the 2021 ESPP. An aggregate of 100,000 shares of the Company’s class A common stock has been authorized for issuance under the 2021 ESPP. During the three months ended March 31, 2022, 7,450 shares of class A common stock were issued in connection with the 2021 ESPP. As of March 31, 2022, 87,938 shares of the Company’s class A common stock remained available for issuance under the 2021 ESPP.

For the three months ended March 31, 2022 and 2021, the Company recognized approximately $0.6 million and $0.4 million, respectively, in share-based compensation expense related to the 2021 ESPP. As of March 31, 2022, there was approximately $0.8 million of total unrecognized share-based compensation expense related to the 2021 ESPP. As of March 31, 2022, the Company expects to recognize this remaining share-based compensation expense over a period of approximately 0.4 years.

During the three months ended March 31, 2022, the Company recognized tax expense on exercises of stock options and vesting of share-settled restricted stock units of approximately $0.1 million and tax benefits on share-based compensation expense of approximately $2.9 million, for a total tax benefit of $2.8 million related to the Company’s equity plans. During the three months ended March 31, 2021, the Company recognized tax benefits on exercises of stock options of approximately $22.1 million and tax benefits on share-based compensation expense of approximately $1.3 million, for a total tax benefit of $23.4 million related to the Company’s equity plans.