Stock-based compensation expense was $85 million in 2021, $80 million in 2020 and $76 million in 2019. The Company recognized income tax benefits related to stock-based compensation of $16 million in 2021, $17 million in 2020 and $19 million in 2019.

The Company’s equity incentive compensation plan allows for the issuance of various forms of stock-based compensation, including stock options, restricted stock and restricted stock units, including performance-based awards. At December 31, 2021 and 2020, respectively, there were 2,299,502 and 3,100,665 shares available for future grant under the Company’s equity incentive compensation plan.

Stock awards granted to employees are comprised of restricted stock and restricted stock units. Stock awards generally vest over three years. The Company may issue shares from treasury stock to the extent available or issue new shares. There were no restricted shares issued in 2021, 2020 or 2019. The number of restricted stock units issued was 636,956 in 2021, 480,949 in 2020 and 448,487 in 2019, with a weighted-average grant date fair value of $84 million, $81 million and $74 million, respectively. Unrecognized compensation expense associated with restricted stock units was $27 million as of December 31, 2021 and is expected to be recognized over a weighted-average period of approximately one year.

	Restricted Stock Units Outstanding			Weighted- Average Grant Price		Restricted Stock Outstanding			Weighted- Average Grant Price

Unvested at January 1, 2021		816,950		$	169.60		13,550		$	162.50
Granted		636,956			132.85		—			—
Vested		(379,155	)		170.80		(9,474	)		162.57
Cancelled		(36,059	)		149.61		—			—
Unvested at December 31, 2021		1,038,692		$	147.32		4,076		$	162.35

Stock options granted to employees generally vest over three years and are exercisable over terms not exceeding ten years and one day. The Company granted 178,441, 187,088 and 164,244 stock options in 2021, 2020 and 2019, respectively. The weighted-average grant date fair value of options granted was $5 million in each of 2021, 2020 and 2019. The Company used an option pricing model to estimate the grant date present value of stock options granted.

				Weighted-Average
	Stock Options Outstanding			Exercise Price		Life (In Years)		Aggregate Intrinsic Value (In thousands)

Outstanding at January 1, 2021		465,423		$	174.11
Granted		178,441			132.47
Exercised		(2,699	)		113.06
Expired		(5,301	)		169.24
Outstanding at December 31, 2021		635,864		$	162.73		7.8	$	3,762
Exercisable at December 31, 2021		282,081		$	177.02		6.9	$	—

For 2021, 2020 and 2019, M&T received $305,000, $3 million and $9 million, respectively, in cash from the exercise of stock options. The intrinsic value of stock options exercised and the related tax benefits realized by the Company were not material in any of those three years. As of December 31, 2021, the amount of unrecognized compensation cost related to non-vested stock options was not material. The total grant date fair value of stock options vested during 2021, 2020 and 2019 was not material. Upon the exercise of stock options, the Company may issue shares from treasury stock to the extent available or issue new shares.

The stock purchase plan provides eligible employees of the Company with the right to purchase shares of M&T common stock at a discount through accumulated payroll deductions. In connection with the employee stock purchase plan, shares of M&T common stock issued were 95,147 in 2021, 77,170 in 2020 and 71,676 in 2019. As of December 31, 2021, there were 2,138,434 shares available for issuance under the plan. M&T received cash for shares purchased through the employee stock purchase plan of $11 million in each of 2021 and 2019, and $12 million in 2020, Compensation expense recognized for the stock purchase plan was not material in 2021, 2020 or 2019.

The Company provided a deferred bonus plan pursuant to which eligible employees could elect to defer all or a portion of their annual incentive compensation awards and allocate such awards to several investment options, including M&T common stock. Participants could elect the timing of distributions from the plan. Such distributions are payable in cash with the exception of balances allocated to M&T common stock which are distributable in the form of M&T common stock. Shares of M&T common stock distributable pursuant to the terms of the deferred bonus plan were 13,319 and 14,304 at December 31, 2021 and 2020, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet.

The Company maintains compensation programs for members of the Company’s boards of directors and its regional director advisory councils that provides for a portion of their compensation to be received in shares or restricted stock units. In 2021, 28,646 shares were issued under such programs.

Through acquisitions, the Company assumed obligations to issue shares of M&T common stock related to deferred directors compensation plans. Shares of common stock issuable under such plans were 2,450 and 3,809 at December 31, 2021 and 2020, respectively. The obligation to issue shares is included in “common stock issuable” in the consolidated balance sheet.