Stock options generally vest ratably over four years. Weighted average option fair values and assumptions for the periods specified are disclosed below. The fair value of each option grant was estimated on the date of the grant using the Binomial lattice option pricing model.


	Three Months Ended March 31,
	2021	2020
Weighted average fair value of grants	$38.59	$34.34
Dividend yield	1.01%	1.15%
Volatility	23.73%	22.01%
Risk-free interest rate	0.09% - 1.57%	1.43% - 1.68%
Expected life (in years)	5.74	5.80


	Three Months Ended March 31,
		2021		2020
Cost of goods sold		$	227	$	185
Selling, general and administrative expenses		2,694		3,145
Total expense before income taxes		2,921		3,330
Income tax benefit		(273)		(367)
Total expense after income taxes		$	2,648	$	2,963

A summary of the Company’s stock option activity as of March 31, 2021 and changes during the three months ended March 31, 2021 are presented in the following table:


Stock Options	Shares	Weighted Average Price		Weighted-Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding at January 1, 2021	963,726	$	125.70	6.94	$	70,829,529
Granted	266,985	197.12
Exercised	(34,500)	93.65
Forfeited	(10,191)	160.30
Outstanding at March 31, 2021	1,186,020	$	142.42	7.47	$	79,349,107
Vested and expected to vest as of March 31, 2021	1,117,282	$	140.14	7.36	$	77,293,221
Exercisable at March 31, 2021	589,346	$	107.82	5.86	$	59,819,281

Restricted stock awards generally cliff vest after three years for employees and non-employee directors. Unvested restricted stock carries dividend and voting rights and the sale of the shares is restricted prior to the date of vesting. A summary of the Company’s restricted stock activity as of March 31, 2021 and changes during the three months ended March 31, 2021 are presented as follows:


Restricted Stock	Shares	Weighted-Average Grant Date Fair Value
Unvested at January 1, 2021	111,300	$	147.13
Granted	22,535	197.05
Vested	(18,909)	132.53
Forfeited	(2,610)	158.07
Unvested at March 31, 2021	112,316	$	159.73

Dividends are paid on restricted stock awards and their fair value is equal to the market price of the Company’s stock at the date of the grant.


	Three Months Ended March 31,
		2021		2020
Cost of goods sold		$	167	$	109
Selling, general and administrative expenses		1,446		982
Total expense before income taxes		1,613		1,091
Income tax benefit		(336)		(229)
Total expense after income taxes		$	1,277	$	862

The Company also maintains a cash-settled share based compensation plan for certain employees. Cash-settled restricted stock awards generally cliff vest after three years. Cash-settled restricted stock awards are recorded at fair value on a quarterly basis using the market price of the Company’s stock on the last day of the quarter. A summary of the Company’s unvested cash-settled restricted stock activity as of March 31, 2021 and changes during the three months ended March 31, 2021 are presented in the following table:


Cash-Settled Restricted Stock	Shares	Weighted-Average Fair Value
Unvested at January 1, 2021	63,940	$	199.20
Granted	19,480	197.10
Vested	(19,806)	196.77
Forfeited	(395)	209.32
Unvested at March 31, 2021	63,219	$	209.32

Dividend equivalents are paid on certain cash-settled restricted stock awards. Total compensation cost for cash-settled restricted stock is as follows:


	Three Months Ended March 31,
		2021		2020
Cost of goods sold		$	210	$	71
Selling, general and administrative expenses		1,270		189
Total expense before income taxes		1,480		260
Income tax benefit		(113)		(16)
Total expense after income taxes		$	1,367	$	244

Weighted average performance share unit fair values and assumptions for the period specified are disclosed below. The performance share units are market condition awards and have been assessed at fair value on the date of grant using a Monte Carlo simulation model.


	Three Months Ended March 31,
	2021	2020
Weighted average fair value of grants	$247.49	$224.14
Dividend yield	—%	—%
Volatility	28.6%	19.5%
Risk-free interest rate	0.33%	1.30%
Expected life (in years)	2.93	2.94

A summary of the Company’s performance share unit activity as of March 31, 2021 and changes during the three months ended March 31, 2021 are presented in the following table:


Performance Share Units	Shares	Weighted-Average Grant Date Fair Value
Unvested at January 1, 2021	58,695	$	218.16
Granted	29,020	247.49
Vested	—	—
Forfeited	(1,590)	212.77
Unvested at March 31, 2021	86,125	$	227.13

On December 31, 2020, 24,305 performance share units vested. Based on the Company’s relative total shareholder return rank during the three year period ended December 31, 2020, the Company achieved a 201% payout factor and issued 48,867 common shares in February 2021 for awards that vested in 2020.


	Three Months Ended March 31,
		2021		2020
Cost of goods sold		$	—	$	—
Selling, general and administrative expenses		1,738		2,049
Total expense before income taxes		1,738		2,049
Income tax benefit		(33)		(49)
Total expense after income taxes		$	1,705	$	2,000

The Company’s policy is to recognize compensation cost on a straight-line basis, assuming forfeitures, over the requisite service period for the entire award. Classification of stock compensation cost within the Condensed Consolidated Statements of Operations is consistent with classification of cash compensation for the same employees.

As of March 31, 2021, there was $14.7 million of total unrecognized compensation cost related to stock options that is expected to be recognized over a weighted-average period of 1.4 years, $7.5 million of total unrecognized compensation cost related to restricted stock that is expected to be recognized over a weighted-average period of 1.1 years, $5.6 million of total unrecognized compensation cost related to cash-settled restricted shares that is expected to be recognized over a weighted-average period of 1.2 years and $8.4 million of total unrecognized compensation cost related to performance share units that is expected to be recognized over a weighted-average period of 1.1 years.