Our board of directors has authorized a share repurchase program of our Class A common stock, which commenced in January 2017 and does not have an expiration date. As of December 31, 2022, $10.87 billion remained available and authorized for repurchases under this program. In January 2023, an additional $40 billion of repurchases was authorized under this program. During the nine months ended September 30, 2023, we repurchased and subsequently retired 72 million shares of our Class A common stock for an aggregate amount of $13.71 billion, including $65 million related to the 1% excise tax on net share repurchases as a result of the Inflation Reduction Act of 2022. As of September 30, 2023, $37.22 billion remained available and authorized for repurchases.

The timing and actual number of shares repurchased under the repurchase program depend on a variety of factors, including price, general business and market conditions, and other investment opportunities. Shares may be repurchased through open market purchases or privately negotiated transactions, including through the use of trading plans intended to qualify under Rule 10b5-1 under the Securities Exchange Act of 1934, as amended.

In December 2022, our board of directors approved an amendment to our 2012 Equity Incentive Plan (Amended 2012 Plan) to increase the number of shares reserved for issuance under the Amended 2012 Plan by 425 million shares, effective March 1, 2023 (Plan Amendment). The Plan Amendment was also approved by holders of a majority of the voting power of our outstanding capital stock in December 2022. As of September 30, 2023, there were 488 million shares of our Class A common stock reserved for future issuance under our Amended 2012 Plan.

The following table summarizes our share-based compensation expense, which consists of the RSU expense, by line item in our condensed consolidated statements of income (in millions):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Cost of revenue	$	183	$	209	$	536	$	582
Research and development	2,881		2,447		8,635		6,995
Marketing and sales	219		260		727		766
General and administrative	209		218		705		641
Total share-based compensation expense	$	3,492	$	3,134	$	10,603	$	8,984


	Number of Shares	Weighted-Average Grant Date Fair Value Per Share
	(in thousands)
Unvested at December 31, 2022	127,110	$	216.93
Granted	108,735	$	198.34
Vested	(49,079)	$	210.58
Forfeited	(22,063)	$	210.81
Unvested at September 30, 2023	164,703	$	207.37

The fair value as of the respective vesting dates of RSUs that vested during the three months ended September 30, 2023 and 2022 was $5.23 billion and $2.59 billion, respectively, and $11.97 billion and $7.77 billion during the nine months ended September 30, 2023 and 2022, respectively. The income tax benefit recognized related to awards vested during the three months ended September 30, 2023 and 2022 was $1.11 billion and $543 million, respectively, and $2.55 billion and $1.64 billion during the nine months ended September 30, 2023 and 2022, respectively.