Our 2014 Long Term Stock Incentive Plan (the "2014 Plan") provides for the issuance of stock-based incentives in various forms to our employees and non-employee Directors. At December 31, 2023, outstanding stock-based incentives were in the form of restricted stock units, performance restricted stock units, stock options, long-term stock awards, phantom stock awards and stock appreciation rights ("SARs").


	Year Ended December 31,
	2023		2022		2021
Restricted stock units	$	15	$	32	$	28
Performance restricted stock units	3		3		10
Stock options	5		7		7
Long-term stock awards	3		6		10
Phantom stock awards and stock appreciation rights	5		1		6
Total	$	31	$	49	$	61

At December 31, 2023, 11.3 million shares of our common stock were available under the 2014 Plan for the granting of restricted stock units, performance restricted stock units, stock options and long-term stock awards.

Restricted Stock Units. Restricted stock units are granted to our key employees and non-employee Directors. These grants did not cause net share dilution due to our practice of repurchasing and retiring an equal number of shares in the open market.


	Year Ended December 31,
	2023			2022			2021
	Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares	Weighted Average Grant Date Fair Value
Unvested restricted stock units at January 1	1,154	$	57	934	$	54	435	$	47
Granted	205	56		621	59		670	57
Vested	(532)	55		(351)	53		(142)	47
Forfeited	(32)	58		(50)	54		(29)	54
Unvested restricted stock units at December 31	796	$	57	1,154	$	57	934	$	54

At December 31, 2023, 2022, and 2021 there was $11 million, $17 million, and $15 million, respectively, of unrecognized compensation expense related to unvested restricted stock units; such units had a weighted average remaining vesting period of two years at December 31, 2023, 2022, and 2021.

Performance Restricted Stock Units. Under our Long Term Incentive Program, we grant performance restricted stock units to certain senior executives. These performance restricted stock units will vest and share awards will be issued at no cost to the employees, subject to our achievement over a three-year period of specified return on invested capital performance goals, an earning per share metric, and, beginning with the 2023 grant, a relative total shareholder return metric that have been established by our Compensation Committee for the performance period. To receive the award, the recipient must be employed through the share award date. Performance restricted stock units are granted at a target number; based on our performance, the number of performance restricted stock units that vest can be adjusted downward to zero and upward to a maximum of 200 percent of the target number.

During 2023, we granted approximately 99,000 performance restricted stock units with a grant date fair value of approximately $52 per share, approximately 253,000 performance restricted stock units were issued and no performance restricted stock units were forfeited. At December 31, 2023, there were approximately 59,000 shares vested but unissued. During 2022, we granted approximately 92,000 performance restricted stock units with a grant date fair value of approximately $55 per share, approximately 168,000 performance restricted stock units were issued and no performance restricted stock units were forfeited. At December 31, 2022, there were approximately 255,000 shares vested but unissued. During 2021, we granted approximately 85,000 performance restricted stock units with a grant date fair value of approximately $53 per share, approximately 105,000 performance restricted stock units were issued and no performance restricted stock units were forfeited. At December 31, 2021, there were approximately 186,000 shares vested but unissued.

Stock Options. Stock options are granted to certain key employees. The exercise price equals the market price of our common stock at the grant date and the stock options expire no later than 10 years after the grant date.


	Year Ended December 31,
	2023			2022			2021
	Number of Shares	Weighted Average Exercise Price		Number of Shares	Weighted Average Exercise Price		Number of Shares	Weighted Average Exercise Price
Outstanding stock options at January 1	2,988	$	39	2,692	$	37	2,488	$	33
Granted	228	57		338	59		332	56
Exercised	(940)	29		(32)	34		(128)	25
Forfeited	(22)	36		(10)	37		—	11
Outstanding stock options at December 31	2,254	$	45	2,988	$	39	2,692	$	37

The aggregate intrinsic value is calculated using our stock price at each respective date, less the exercise price (grant date price) multiplied by the number of shares. The aggregate intrinsic value for options exercised during 2023, 2022 and 2021 was $26 million, $1 million and $5 million, respectively. The weighted-average remaining term for options outstanding at December 31, 2023, 2022 and 2021 was six years, five years and six years, respectively.


	Year Ended December 31,
	2023						2022						2021
	Vested and Expected to Vest Stock Options			Exercisable (Vested) Stock Options			Vested and Expected to Vest Stock Options			Exercisable (Vested) Stock Options			Vested and Expected to Vest Stock Options			Exercisable (Vested) Stock Options
Number of shares	2,248			1,621			2,966			2,051			2,617			1,606
Weighted average exercise price	$	45		$	42		$	39		$	34		$	36		$	31
Aggregate intrinsic value	$	48	million	$	41	million	$	30	million	$	28	million	$	89	million	$	63	million
Weighted-average remaining term	6 years			5 years			5 years			4 years			6 years			5 years

At December 31, 2023, 2022 and 2021, there was $1 million, $1 million and $4 million, respectively, of unrecognized compensation expense (using the Black-Scholes option pricing model at the grant date) related to unvested stock options; such options had a weighted average remaining vesting period of two years, one year and two years at December 31, 2023, 2022 and 2021, respectively.


	Year Ended December 31,
	2023			2022			2021
Weighted average grant date fair value	$	16.91		$	14.66		$	13.61
Risk-free interest rate	3.95		%	1.90		%	0.75		%
Dividend yield	2.02		%	1.89		%	1.67		%
Volatility factor	31.00		%	29.00		%	30.00		%
Expected option life	6 years			6 years			6 years


At December 31, 2023,
	Option Shares Outstanding				Option Shares Exercisable
	Range of Prices	Number of Shares	Weighted Average Remaining Option Term	Weighted Average Exercise Price	Number of Shares	Weighted Average Exercise Price
$	22 - 26	256	2	$25	256	$25
$	27 - 36	538	4	$35	469	$35
$	37 - 60	1,459	7	$53	896	$50
$	22 - 60	2,254	6	$45	1,621	$42


	Year Ended December 31,
	2023			2022			2021
	Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares	Weighted Average Grant Date Fair Value
Unvested stock award shares at January 1	273	$	38	608	$	37	1,125	$	36
Vested	(191)	40		(324)	37		(491)	34
Forfeited	(3)	36		(11)	38		(26)	36
Unvested stock award shares at December 31	79	$	36	273	$	38	608	$	37

At December 31, 2023, the total unrecognized compensation expense related to unvested stock awards was insignificant and the unvested stock awards will vest in 2024. At December 31, 2022 and 2021, there was $3 million and $10 million, respectively, of total unrecognized compensation expense related to unvested stock awards; such awards had a weighted average remaining vesting period at December 31, 2022 and 2021 of one year and two years, respectively.

We recognized expense of $5 million, $1 million and $6 million in 2023, 2022 and 2021, respectively, related to phantom stock awards. In 2023, 2022 and 2021, we granted approximately 57,000, 74,000, and 82,000 shares, respectively, of phantom stock awards with an aggregate fair value of $3 million, $4 million and $5 million in 2023, 2022 and 2021, respectively, and paid cash of $4 million in 2023, $4 million in 2022 and $3 million in 2021 to settle phantom stock awards.