The Company records compensation expense for employee stock options based on the estimated fair value of the options on the date of grant using the Black-Scholes option-pricing model with the assumptions included in the table below. The Company uses a combination of historical data and historical volatility to establish the expected volatility, as well as to estimate the expected option life. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for the estimated life of the option. The following assumptions were used to estimate the fair value of options granted using the Black-Scholes option-pricing model:



									For the six
									months ended
									June 30, 2023

Risk free interest rate									3.96%
Dividend yield									1.5%
Expected volatility									30%
Expected lives									4.4 years

The following table summarizes the Company’s activities with respect to its stock option plans for the six months ended June 30, 2023 as follows (dollars and shares in thousands, except for per share data):



		Weighted-		Weighted-Average
		Average		Remaining
	Number	Exercise Price		Contractual	Aggregate
	of Shares	Per Share		Life (in years)	Intrinsic Value
Outstanding at December 31, 2022	1,673	$	161.02
Granted	20	$	224.24
Exercised	(176)	$	127.05
Forfeited/canceled	(8)	$	235.41
Outstanding at June 30, 2023	1,509	$	165.42	2.2	$	101,124
Exercisable at June 30, 2023	1,479	$	163.71	2.0	$	100,973
Unvested at June 30, 2023	30	$	254.38	9.4	$	151

The weighted-average per share fair value of options granted during the six months ended June 30, 2023 was $58.95. The total intrinsic value for options exercised during the six months ended June 30, 2023 was $23.9 million.

The following table summarizes the Company’s RSU and PSU activity for the six months ended June 30, 2023:



	RSUs			PSUs ⁽¹⁾
		Weighted-Average			Weighted-Average
	Number of	Grant Date Fair		Number of	Grant Date Fair
	Shares	Value per Share		Shares	Value per Share
	(in thousands)			(in thousands)
Outstanding at December 31, 2022	222	$	280.66	429	$	332.18
Granted	171	$	255.36	96	$	263.35
PSU adjustment ⁽²⁾	—	$	—	65	$	302.96
Vested	(117)	$	263.75	(207)	$	345.08
Forfeited/canceled	(11)	$	278.05	(14)	$	298.10
Outstanding at June 30, 2023	265	$	271.40	369	$	298.65

(1)PSUs represent the target number of shares granted that are issuable at the end of the three year performance period. Fair value for a portion of the PSUs was calculated using a Monte Carlo simulation model.