Prior to its expiration, the Company maintained the 2013 Stock Incentive Plan (as amended, the “2013 Equity Plan”), under which the Company’s employees, officers, and directors were awarded various types of share-based compensation, including options to purchase shares of the Company’s class A common stock, restricted stock units, and other stock-based awards. In May 2023, the 2013 Equity Plan expired and no new awards may be granted under the 2013 Equity Plan, although awards previously granted under the 2013 Equity Plan will continue to remain outstanding in accordance with their terms.

The Company maintains the 2023 Equity Incentive Plan, the “2023 Equity Plan”, under which the Company’s employees, officers, directors, and other eligible participants may be awarded various types of share-based compensation, including options to purchase shares of the Company’s class A common stock, restricted stock units, performance stock units, and other stock-based awards. An aggregate of up to 1,932,703 shares of the Company’s class A common stock were authorized for issuance under the 2023 Equity Plan. As of March 31, 2024, there were 231,007 shares of class A common stock reserved and available for future issuance under the 2023 Equity Plan. The 2013 Equity Plan and the 2023 Equity Plan together are referred to herein as the “Stock Incentive Plans.”

As of March 31, 2024, there were options to purchase 702,571 shares of class A common stock outstanding under the Stock Incentive Plans.

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, 2024:


	Stock Options Outstanding
				Weighted Average		Aggregate		Weighted Average
				Exercise Price		Intrinsic		Remaining Contractual
	Shares			Per Share		Value		Term (Years)
Balance as of January 1, 2024		1,294		$	286.78
Granted		9		$	1,599.29
Exercised		(583	)	$	233.42	$	468,114
Forfeited/Expired		(17	)	$	447.47
Balance as of March 31, 2024		703		$	343.31
Exercisable as of March 31, 2024		385		$	294.39	$	542,263		4.8
Expected to vest as of March 31, 2024		318		$	402.45	$	414,114		8.0
Total		703		$	343.31	$	956,377		6.2

Stock options outstanding as of March 31, 2024 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, 2024
			Weighted Average		Weighted Average
			Exercise Price		Remaining Contractual
Range of Exercise Prices per Share	Shares		Per Share		Term (Years)
$121.43 - $200.00		280	$	144.01		3.9
$200.01 - $300.00		108	$	251.21		8.6
$300.01 - $400.00		3	$	301.63		9.2
$400.01 - $500.00		180	$	411.49		7.8
$600.01 - $700.00		123	$	691.23		6.9
$1,500.01 - $1,599.29		9	$	1,599.29		10.0
Total		703	$	343.31		6.2

An aggregate of 109,250 stock options with an aggregate grant date fair value of $32.7 million vested during the three months ended March 31, 2024. The weighted average grant date fair value of stock option awards using the Black-Scholes valuation model was $1,114.42 for each share subject to a stock option granted during the three months ended March 31, 2024, based on the following assumptions:

No stock option awards were granted during the three months ended March 31, 2023. For the three months ended March 31, 2024 and 2023, the Company recognized approximately $9.8 million and $12.9 million, respectively, in share-based compensation expense from stock options granted under the Stock Incentive Plans. As of March 31, 2024, there was approximately $66.5 million of total unrecognized share-based compensation expense related to unvested stock options, which the Company expects to recognize over a weighted average vesting period of approximately 2.1 years.

As of March 31, 2024, there were 196,830 share-settled restricted stock units outstanding under the Stock Incentive Plans. 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
	Units			Intrinsic Value
Balance as of January 1, 2024		185
Granted		30
Vested		(6	)	$	4,307
Forfeited		(12	)
Balance as of March 31, 2024		197
Expected to vest as of March 31, 2024		197		$	335,509

During the three months ended March 31, 2024, 6,002 share-settled restricted stock units having an aggregate grant date fair value of $3.2 million vested, and 1,889 shares were withheld to satisfy tax obligations, resulting in 4,113 issued shares. During the three months ended March 31, 2023, 5,780 share-settled restricted stock units having an aggregate grant date fair value of $3.4 million vested, and 1,963 shares were withheld to satisfy tax obligations, resulting in 3,817 issued shares. The weighted average grant date fair value of share-settled restricted stock units granted during the three months ended March 31, 2024 and 2023 was $1,451.66 and $258.65, respectively, based on the fair value of the Company’s class A common stock.

For the three months ended March 31, 2024 and 2023, the Company recognized approximately $4.7 million and $3.4 million, respectively, in share-based compensation expense from share-settled restricted stock units granted under the Stock Incentive Plans. As of March 31, 2024, there was approximately $84.1 million of total unrecognized share-based compensation expense related to unvested share-settled restricted stock units, which the Company expects to recognize over a weighted average vesting period of approximately 3.3 years.

As of March 31, 2024, there were 30,285 performance stock units outstanding under the 2023 Equity Plan. The following table summarizes the Company’s performance stock unit activity (in thousands) for the periods indicated:


	Share-Settled Performance Stock Units Outstanding
				Aggregate
	Units			Intrinsic Value
Balance as of January 1, 2024		25
Granted		6
Vested		0		$	0
Forfeited		(1	)
Balance as of March 31, 2024		30
Expected to vest as of March 31, 2024		30		$	103,245

The weighted average grant date fair value of performance stock units using the Monte-Carlo simulation model was $3,071.27 for each performance stock unit granted during the three months ended March 31, 2024 based on the following assumptions:


	Three months ended
	March 31,
	2024
Expected term of awards in years		3.0
Expected volatility		92.7	%
Risk-free interest rate		4.4	%
Expected dividend yield		0.0	%

No performance stock units were granted during the three months ended March 31, 2023. No performance stock units vested during the three months ended March 31, 2024. For the three months ended March 31, 2024, the Company recognized approximately $1.1 million in share-based compensation expense from performance stock units granted under the 2023 Equity Plan. As of March 31, 2024, there was approximately $25.8 million of total unrecognized share-based compensation expense related to unvested performance stock units, which the Company expects to recognize over a weighted average vesting period of approximately 2.7 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, 2024 and 2023, the Company recognized approximately $1.8 million and $0.7 million, respectively, in share-based compensation expense from other stock-based awards and cash-settled restricted stock units. As of March 31, 2024, there was approximately $0.7 million of total unrecognized share-based compensation expense related to other stock-based awards and cash-settled restricted stock units, which the Company expects to recognize over a weighted average vesting period of approximately 0.9 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 in 6-month offering periods commencing on each March 1 and September 1. 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, 2024, 6,932 shares of class A common stock were issued in connection with the 2021 ESPP. As of March 31, 2024, 52,675 shares of the Company’s class A common stock remained available for issuance under the 2021 ESPP.

For the three months ended March 31, 2024 and 2023, the Company recognized approximately $0.4 million and $0.6 million, respectively, in share-based compensation expense related to the 2021 ESPP. As of March 31, 2024, there was approximately $0.7 million of total unrecognized share-based compensation expense related to the 2021 ESPP, which the Company expects to recognize over a period of approximately 0.4 years.

The following table summarizes the tax benefit related to the Company’s equity plans (in thousands) for the three months ended March 31, 2024 and 2023:


	Three Months Ended
	March 31,
	2024			2023
Tax benefit related to:
Share-based compensation expense	$	(4,192	)	$	(3,225	)
Exercises of stock options and vesting of share-settled restricted stock units		(104,306	)		(85	)
Total tax benefit related to the Company's equity plans	$	(108,498	)	$	(3,310	)