In August 2011, we established the Groupon, Inc. 2011 Stock Plan (the "2011 Plan"), as amended in November 2013, May 2014, June 2016, April 2019, and June 2022, under which options, restricted stock units and performance stock units for up to 11,875,000 shares of common stock were authorized for future issuance to employees, consultants and directors.

The 2011 Plan is administered by the Compensation Committee of the Board (the "Compensation Committee"). As of December 31, 2022, 3,266,298 shares of common stock were available for future issuance under the 2011 Plan.

The stock-based compensation expense related to stock awards issued under the 2011 Plan and acquisition-related awards are presented within the following line items of the Consolidated Statements of Operations for the years ended December 31, 2022, 2021 and 2020 (in thousands):


	Year Ended December 31,
	2022		2021		2020
Cost of revenue	$	395	$	585	$	662
Marketing	1,054		748		1,522
Selling, general and administrative	28,557		31,836		36,826
Restructuring and related charges	—		—		1,735
Total stock-based compensation expense	$	30,006	$	33,169	$	40,745

We capitalized $3.4 million, $3.7 million and $4.5 million of stock-based compensation for the years ended December 31, 2022, 2021 and 2020, in connection with internally-developed software and cloud computing arrangements.

The Groupon, Inc. 2012 Employee Stock Purchase Plan, as amended, authorizes us to grant up to 1,000,000 shares of common stock under that plan. For the years ended December 31, 2022, 2021 and 2020, 83,551, 49,399 and 69,371 shares of common stock were issued under the ESPP.

The restricted stock units granted under the 2011 Plan generally have vesting periods between one and four years and are amortized on a straight-line basis over their requisite service period.


	Restricted Stock Units	Weighted- Average Grant Date Fair Value (per share)
Unvested at December 31, 2021	2,205,235	$	31.06
Granted	2,720,990	16.95
Vested	(1,080,881)	32.22
Forfeited	(969,255)	24.82
Unvested at December 31, 2022	2,876,089	$	19.33

The weighted-average grant date fair value of restricted stock units granted in 2021 and 2020 was $31.48 and $24.92. The fair value of restricted stock units that vested during each of the three years ended December 31, 2022, 2021 and 2020 was $15.6 million, $48.8 million and $19.2 million. As of December 31, 2022, $39.3 million of unrecognized compensation costs related to unvested employee restricted stock units are expected to be recognized over a remaining weighted-average period of 1 year.

We have previously granted performance share units under the 2011 Plan that vest in shares of our common stock upon the achievement of financial and operational targets specified in the respective award agreement ("Performance Share Units"). Our existing Performance Share Units are subject to continued employment through the performance period dictated by the award and certification by the Compensation Committee of the Board that the specified performance conditions have been achieved.


	Performance Share Units	Weighted-Average Grant Date Fair Value (per unit)
Unvested at December 31, 2021	37,763	$	28.39
Granted	—	—
Vested	(20,494)	31.97
Forfeited	—	—
Unvested at December 31, 2022	17,269	$	24.13

Maximum shares issuable upon vesting at December 31, 2022	17,269

As of December 31, 2022, we have recognized substantially all expense related to the unvested Performance Share Units, which vested in the first quarter of 2023.

We have also previously granted performance share units subject to a market condition ("Market-based Performance Share Units"). As of December 31, 2022, 24,335 Market-based Performance Share Units were forfeited and 33,333 Market-based Performance Share Units expired as the market conditions were not met. No Market-based Performance Share Units remain unvested and all related compensation costs have been recognized as of December 31, 2022.

We have a 401(k) defined contribution retirement savings plan covering substantially all domestic employees. Each participant may elect to defer a portion of his or her compensation subject to certain limitations. We contribute up to 50% of the first 6% of eligible compensation contributed to the plan, subject to a 3 year graded vesting schedule. We also have several foreign defined contribution plans, which require us to contribute a percentage of participating employee's salary according to local regulations. During the years ended December 31, 2022, 2021 and 2020, our contributions for all plans were $5.8 million, $6.7 million and $6.6 million.