The Company has outstanding stock-based compensation awards granted under the 2013 Stock Incentive Plan (“2013 Plan”) and the 2017 Omnibus Incentive Plan (“2017 Plan”) as described in Note 18, “Stock-Based Compensation Plans” to the consolidated financial statements in its 2021 Form 10-K.

The Company’s stock-based compensation awards are typically granted in the first quarter of the year and primarily consist of stock options, restricted stock units and performance share units. Eligible employees were also granted restricted stock units, during the three months ended September 30, 2020, that vest ratably over two years, subject to the passage of time and the employee's continued employment during such period. In some instances, such as death, awards may vest concurrently with or following an employee's termination.

Stock-based compensation expense for the three month periods ended March 31, 2022 and 2021 are included in “Cost of sales” and “Selling and administrative expenses” in the Condensed Consolidated Statements of Operations and are as follows.


	For the Three Month Period Ended March 31,
	2022		2021
Stock-based compensation expense recognized in:
Continuing operations	$	19.8	$	21.6
Discontinued operations	—		2.5
Total stock-based compensation expense	$	19.8	$	24.1

In the three month period ended March 31, 2022, the $19.8 million of stock-based compensation expense included expense for equity awards granted under the 2013 and 2017 Plan of $21.0 million and a decrease in the liability for stock appreciation rights (“SAR”) of $1.2 million. Of the $21.0 million of expense for equity awards granted under the 2013 Plan and 2017 Plan, $13.0 million related to the $150 million equity grant to nearly 16,000 employees worldwide made in the third quarter of 2020 (“All-Employee Equity Grant”).

As of March 31, 2022, there was $111.8 million of total unrecognized compensation expense related to outstanding stock options, restricted stock unit awards and performance stock unit awards.

Stock options are granted to employees with an exercise price equal to the fair value of the Company’s per share common stock on the date of grant. Stock option awards typically vest over four or five years and expire ten years from the date of grant.

A summary of the Company’s stock option (including SARs) activity for the three month period ended March 31, 2022 is presented in the following table (underlying shares in thousands).


	Shares	Weighted-Average Exercise Price (per share)
Stock options outstanding as of December 31, 2021	6,746	$	21.76

Granted	731	53.09
Exercised or settled	(194)	23.66
Forfeited	(46)	32.53
Expired	—	—
Stock options outstanding as of March 31, 2022	7,237	24.81

Vested as of March 31, 2022	5,058	18.16

The following assumptions were used to estimate the fair value of options granted during the three month periods ended March 31, 2022 and 2021 using the Black-Scholes option-pricing model.


	For the Three Month Period Ended March 31,
Assumptions	2022		2021
Expected life of options (in years)	6.3		6.3
Risk-free interest rate	1.9	%	0.9	%
Assumed volatility	38.3	%	39.4	%
Expected dividend rate	0.2	%	0.0	%

Restricted stock units are granted to employees and non-employee directors based on the market price of the Company’s common stock on the grant date and recognized in compensation expense over the vesting period. A summary of the Company’s restricted stock unit activity for the three month period ended March 31, 2022 is presented in the following table (underlying shares in thousands).


	Shares	Weighted-Average Grant-Date Fair Value
Non-vested as of December 31, 2021	2,677	$	34.08

Granted	460	53.09
Vested	(427)	31.88
Forfeited	(72)	34.20
Non-vested as of March 31, 2022	2,638	37.74

Performance share units are granted to employees and are subject to a three year performance period. The number of shares issued at the end of the performance period is determined by the Company’s total shareholder return percentile rank versus the S&P 500 index for the three year performance period. The grant date fair value of these awards is determined using a Monte Carlo simulation pricing model and compensation cost is recognized straight-line over a three year period.

A summary of the Company’s performance stock unit activity for the three month period ended March 31, 2022 is presented in the following table (underlying shares in thousands).


	Shares	Weighted-Average Grant-Date Fair Value
Non-vested as of December 31, 2021	393	$	39.89
Granted	175	63.39
Forfeited	(15)	39.61
Non-vested as of March 31, 2022	553	47.33

The following assumptions were used to estimate the fair value of performance share units granted during the three month periods ended March 31, 2022 and 2021 using the Monte Carlo simulation pricing model.


	For the Three Month Period Ended March 31,
Assumptions	2022		2021
Expected term (in years)	2.9		2.9
Risk-free interest rate	1.7	%	0.2	%
Assumed volatility	36.4	%	36.9	%
Expected dividend rate	0.2	%	—	%