At December 31, 2022, a total of 18,652,998 shares of unissued common stock were authorized for issuance under our stock-based compensation plans. Additionally, a total of 907,014 shares are authorized for issuance under a plan whereby substantially all employees may acquire common stock through payroll deductions at prevailing market prices.

The following table summarizes the status of, and changes in, our stock options during 2022.


	Options	Weighted- average exercise price		Weighted-average remaining contractual term in years
Outstanding at December 31, 2021	2,846,579	$	72.87

Exercised	(628,073)	$	67.79


Outstanding at December 31, 2022	2,218,506	$	74.31	1.7
Exercisable at December 31, 2022	2,218,506	$	74.31	1.7

Compensation and related costs includes a charge for stock option-based compensation expense. There was no stock option-based compensation expense in 2022 and 2021, but, in 2020, we recorded $2.0 million of stock option-based compensation expense.

The total intrinsic value of options exercised was $40.3 million in 2022, $177.2 million in 2021, and $198.3 million in 2020. At December 31, 2022, the aggregate intrinsic value of in-the-money options outstanding was $77.1 million. All outstanding options are exercisable.

The following table summarizes the status of, and changes in, our nonvested restricted shares and restricted stock units during 2022.


	Restricted shares	Restricted stock units	Weighted- average fair value
Nonvested at December 31, 2021	5,720	5,701,865	$	146.87
Time-based grants	8,715	2,191,601	$	121.51
Performance-based grants	—	77,372	$	121.33
Vested (value at vest date was $231.4 million)	(5,720)	(1,877,992)	$	130.49
Nonvested dividend equivalents granted to non-employee directors	—	3,980	$	119.52
Forfeited	—	(195,226)	$	144.00
Nonvested at December 31, 2022	8,715	5,901,600	$	142.37

Nonvested at December 31, 2022 includes performance-based restricted stock units of 371,890. These nonvested performance-based restricted units include 81,123 units for which the performance period has lapsed, and the performance threshold has been met.

Compensation and related costs includes expenses for restricted shares and restricted stock units of $285.4 million in 2022, $274.6 million in 2021, and $244.1 million in 2020.

At December 31, 2022, non-employee directors held 94,939 vested stock units that will convert to common shares upon their separation from the Board.

The following table presents the compensation expense to be recognized over the remaining vesting periods of the stock-based awards outstanding at December 31, 2022. Estimated future compensation expense will change to reflect future grants, changes in the probability of performance thresholds being met, and adjustments for actual forfeitures.


(in millions)
First quarter 2023	$	60.6
Second quarter 2023	59.2
Third quarter 2023	58.0
Fourth quarter 2023	50.7
Total 2023	228.5
2024 through 2028	218.0
Total	$	446.5