In 2016, the Company adopted the 2016 Equity Incentive Plan (as amended, the “2016 Plan”). The 2016 Plan provided for the issuance of restricted stock awards (“RSAs”), RSUs, stock appreciation rights (“SARs”), incentive stock options, non-qualified stock options and other stock-based awards to employees and consultants of the Company and its affiliates and members of the Board of Directors of the Company (the “Board”). Prior to its termination, the number of shares of Class A common stock authorized for issuance under the 2016 Plan was 51,716,934. Only incentive stock options, non-qualified stock options and RSUs were granted under the 2016 Plan.

On May 18, 2021, the Board approved the termination of the 2016 Plan. Any remaining shares of common stock available for issuance under the 2016 Plan as of such date were added to the shares of our Class A common stock reserved for issuance under the Company's 2021 Equity Incentive Award Plan (the “2021 Plan”). Additionally, any shares of common stock subject to awards granted under the 2016 Plan that expire, lapse or are terminated, exchanged for or settled in cash, surrendered, repurchased, canceled without having been fully exercised, or forfeited following the effective date of the 2021 Plan will become available for issuance under the 2021 Plan.

On May 18, 2021, the Board adopted and the stockholders of the Company approved the 2021 Plan and the 2021 Employee Stock Purchase Plan (the “ESPP”).

Upon adoption, 14,592,452 shares of the Company's Class A common stock were reserved for future issuance under the 2021 Plan, which number consists of (a) 10,197,941 shares initially available for issuance and (b) an additional 4,394,511 shares previously reserved for but unissued under the 2016 Plan on the effective date of the 2021 Plan that become available for issuance under the 2021 Plan. The 2021 Plan authorizes the granting of RSAs, RSUs, SARs, incentive stock options, non-qualified stock options, dividend equivalents, and other stock or cash awards to employees and consultants of the Company and its subsidiaries and members of the Board.

In addition to the 2021 Plan, up to 1,605,647 shares of the Company’s Class A common stock may be issued under the ESPP. The ESPP permits eligible employees to purchase shares of the Company's Class A common stock at a 15% discount to the lesser of (i) the fair market value of the Company's Class A common stock on the first trading day of an applicable offering period or (ii) the last trading day of a purchase period in an applicable offering period. As of December 31, 2021 there have been no purchases of the Company's Class A common stock under the ESPP.

All options and SARs granted under the 2021 Plan will generally expire ten years from the date of grant if not exercised. In the event of a termination of employment, any unvested portion of an option will generally be forfeited immediately. Any vested options may generally be exercised within three months, except for (i) instances of termination due to death or disability whereby any vested options may be exercised within one year and (ii) instances of termination “with cause” whereby any vested options are forfeited immediately.

Shares that expire, lapse or are terminated, exchanged for or settled in cash, surrendered, repurchased, canceled without having been fully exercised, or forfeited will become available for future awards under the 2021 Plan. In addition, shares of common stock that are tendered to the Company by a participant to satisfy the applicable exercise or purchase price of an award and/or to satisfy any applicable tax withholding obligation with respect to an award will be added to the number of shares of common stock available for future awards. The 2021 Plan is administered by the Board with respect to awards to non-employee directors and by the Compensation Committee of the Board with respect to other participants.

As of December 31, 2021, the number of shares available for issuance under the 2021 Plan was 13,756,934.

The assumptions that the Company used to determine the grant date fair value of stock options granted were as follows, presented on a weighted-average basis:


	December 31,
	2021			2020			2019
Risk free interest rate		1.15	%		0.42	%		1.81	%
Expected volatility		48	%		44	%		57	%
Expected dividend yield		0	%		0	%		0	%
Expected term (in years)		6.25			6.45			6.25

A summary of stock option activity under the Plan, is as follows:


	Stock Options Outstanding
	Number of Shares			Weighted Average Exercise Price (per share)		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2020		39,837,195		$	3.49		8.87	$	101
Granted		3,843,666			19.94
Exercised		(3,346,352	)		0.90
Forfeited		(2,462,829	)		5.82
Outstanding at December 31, 2021		37,871,680		$	5.24		8.02	$	846

Exercisable at December 31, 2021		24,466,168		$	3.44		7.53	$	590

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the common stock as of the end of the period. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2021 and 2020 was $115.1 and $1.2 million, respectively. There were no exercises of stock options for the year ended December 31, 2019.

The weighted-average grant date fair values per share of the Company’s stock options granted during the years ended December 31, 2021, 2020, and 2019 was $10.02, $3.53, and $0.25, respectively. The grant date fair value of stock options vested during the years ended December 31, 2021, 2020 and 2019 was $49.8 million, $4.8 million, and $0.2 million, respectively.

As of December 31, 2021, total unrecognized compensation cost related to unvested stock option awards was $66.0 million, to be recognized over a weighted-average period of 3.3 years.

During the year ended December 31, 2021, the Board determined to accelerate the vesting of certain employee stock option awards, subject to and effective as of the closing of the Company’s IPO, and further subject to the employee's continued service with the Company through the closing of the IPO, as described in our IPO Prospectus. Upon the modification of the stock options, the Company determined no incremental fair value was required to be recorded as the awards would continue to vest both prior to and post modification and the modification of the stock options did not change award valuation inputs or assumptions. The Company recorded $32.8 million of expense during the second quarter of 2021 as a result of the accelerated vesting of stock options.

During the year ended December 31, 2021, in connection with the retirement of the Company’s Chief Financial Officer, the Board determined to accelerate the vesting of certain stock option awards held by the retiring executive and provide that such stock option awards may be exercised for one year following the retirement date. Upon the modification of the stock options, the Company determined that $5.7 million of incremental fair value was required to be recorded related to the 275,000 stock options which were not probable of vesting prior to the modification but concluded to be probable of vesting based on the modified terms of the award. The modification of stock options changed the award valuation inputs, including the remaining term of the award. The Company recorded $5.7 million of expense related to the stock option modification during the fourth quarter of 2021 as a result of the accelerated vesting of stock options.

During the year ended December 31, 2020, the Company granted 5,410,440 RSUs which vest upon the satisfaction of both a service and a performance condition and granted no RSAs. The service condition for these awards is satisfied over four years. The performance condition is satisfied upon the occurrence of a qualifying event, generally defined as a change of control transaction or an initial public offering. The performance condition for these awards was satisfied in connection with the IPO. Upon the satisfaction of the performance condition, the Company recorded $16.0 million of stock-based compensation expense related to these awards and withheld 762,359 shares of common stock, based on the IPO price of $22.00 per share, to satisfy the tax remittances of approximately $16.8 million.

The fair value of RSUs and RSAs vested during the year ended December 31, 2021 was $72.6 million. There were no RSUs or RSAs that vested during the year ended December 31, 2020 or the year ended December 31, 2019.

As of December 31, 2021, total unrecognized compensation cost related to unvested RSAs and RSUs was $33.7 million, to be recognized over a weighted-average period of 2.4 years.

A summary of RSA and RSU activity under the 2016 Plan and 2021 Plan is as follows:


	Number of Shares			Weighted average grant date fair value per share
Unvested restricted stock at December 31, 2020		5,410,440		$	4.51
Granted		1,079,864			31.77
Vested		(2,793,436	)		5.38
Forfeited		(28,700	)		34.18
Unvested restricted stock at December 31, 2021		3,668,168		$	11.65