The Plans provide for the grant of NSOs, ISOs, RSUs and PSUs intended to qualify under Section 422 of the Internal Revenue Code; and the 2000 Plan provides for the grant of NSOs. The Plans authorize awards to the Company’s officers, employees and consultants and to the Company’s directors.

The exercise price per share of an option granted under any of the Plans may not be less than the closing price of a share of the Company’s common stock on the date of grant. The maximum term of an option granted under any of the Plans may not exceed 8 or 10 years. An option may be exercised only when it is vested and, in the case of an option granted to an employee (including an officer), only while he or she remains an employee and for a limited period following the termination of his or her employment. New shares are issued upon exercise of stock options.

In October 2000, our Board of Directors adopted the ESPP, which our stockholders approved in May 2001 and was made effective as of July 1, 2001. The ESPP authorizes 1,799,999 shares of our common stock, which substantially all U.S. employees may purchase through payroll deductions at a price equal to 85% of the fair market values of the stock as of the end of the 6 months offering period. An employee's payroll deductions and stock purchase, may not exceed $5,000 during any offering period. During 2020, 2019, and 2018, 70,120 shares, 97,669 shares and 131,959 shares, respectively, were issued through the ESPP. At December 31, 2020, we had 587,705 shares available for issuance under the ESPP plan.

The following table presents the total stock-based compensation expense resulting from stock option awards, RSUs, PSUs and the ESPP and Canada ESPP included in the Consolidated Statements of Loss:


In millions
	Year Ended December 31,
	2020		2019		2018
SG&A - stock option plans	$	3.2	$	8.0	$	10.8
SG&A - RSUs	15.6		7.8		7.2
SG&A - PSUs	5.9		0.5		5.1
SG&A - ESPP and Canada ESPP	0.8		0.8		1.0
Total pre-tax expense	$	25.5	$	17.1	$	24.1

Options granted to non-employee directors vest in one year and options granted to officers and employees generally vest over five years. Expense related to options with graded vesting is recognized using the straight-line method over the vesting period.


	Number of Options	Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life	Total Aggregate Intrinsic Value
				(in years)	(in millions)
Outstanding as of January 1, 2020	3,967,425	$	96.32
Granted	—	$	—
Exercised	(49,448)	$	54.21
Forfeited	(122,685)	$	71.95
Cancelled or expired	(934,824)	$	102.67
Outstanding as of December 31, 2020	2,860,468	$	96.00	2.50	$	6.7
Exercisable as of December 31, 2020	2,490,182	$	100.50	2.00	$	2.2

At December 31, 2020, there was $3.6 million of total unrecognized compensation expense related to stock options, which is expected to be recognized over a weighted average period of 1.6 years.

The exercise intrinsic value represents the total pre-tax intrinsic value (the difference between the fair value on the trading day the option was exercised and the exercise price associated with the respective option).

There were no stock options granted in the year ended December 31, 2020. The Company uses historical data to estimate expected life and volatility. The fair value of stock options at the time of grant using the Black-Scholes option pricing model was as follows:


	Year Ended December 31,
		2019			2018
Stock options granted (shares)		340,652			430,337
Weighted average fair value at grant date		$	14.41		$	16.79
Assumptions:
Expected term (in years)		4.34			4.89
Expected volatility		30.99		%	25.52		%
Expected dividend yield		0.00		%	0.00		%
Risk free interest rate		2.35		%	2.64		%

The fair value of RSUs is based on the closing price of the Company's common stock on the date of grant and is amortized to expense over the service period. RSUs vest at the end of three or five years. The 2017 Plan includes a share reserve for RSUs granted at a 1-1 ratio while our 2008, 2011 and 2014 Plans reserve at a 2-1 ratio. No RSUs were granted under the 2005 Plan.


	Number of Units	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life	Total Aggregate Intrinsic Value
				(in years)	(in millions)
Non-vested as of January 1, 2020	439,080	$	59.09
Granted	574,712	$	51.82
Vested and Released	(326,797)	$	54.63
Forfeited	(139,760)	$	55.72
Non-vested as of December 31, 2020	547,235	$	54.96	1.10	$	37.9

At December 31, 2020, there was $19.3 million of total unrecognized compensation expense related to RSUs, which is expected to be recognized over a weighted average period of 1.9 years. The fair value of units that vested during the years ended December 31, 2020, 2019, and 2018 was $18.2 million, $5.3 million, and $4.2 million, respectively.

Our executive officers PSU program was introduced in 2017. PSUs issued to executive officers in 2018 and 2019 vest, or not, in three equal annual installments based on the achievement of pre-determined annual earnings per share performance goals as approved by the Compensation Committee. Each of the PSU’s granted represent the right to receive one share of the Company’s common stock at a specified future date.

Our PSU program was expanded in 2020 to include employees in additional levels below executive officer. PSUs issued beginning in 2020 vest, or not, at the end of the three-year period following the grant date based on the achievement of pre-determined annual earnings per share and annual return on invested capital performance goals as approved by the Compensation Committee (each metric is weighted at 50% of the whole). At the end of the three-year period, the results from each of the three years are averaged to calculate one achievement percentage number, and then a relative total shareholder return (rTSR) modifier is applied to that number in order to determine the final share amount, based on Stericycle’s stock’s market performance relative to performance of the S&P MidCap 400 Index. The modifier can adjust the final shares issued by applying a multiplier of 75% - 125%.

In addition, certain employees have been granted PSUs which vest, or not, in four equal annual installments based on the achievement of performance goals related to the Business Transformation, as approved by the Compensation Committee.

Compensation cost for the executive and Business Transformation PSU’s has been recognized based on the estimated achievement of the underlying goals. The number of PSU’s that recipients will ultimately receive will be based upon the Compensation Committee’s review of the actual achievement of these goals. Each of the PSU’s granted represent the right to receive one share of the Company’s common stock at a specified future date.


	Number of Units	Weighted Average Grant Date Fair Value
Non-vested as of January 1, 2020	116,049	$	63.77
Granted	109,006	$	58.09
Vested and Released	(38,885)	$	48.23
Forfeited (including performance goal not achieved)	(94,128)	$	50.58
Non-vested as of December 31, 2020	92,042	$	57.79

The table above reflects the number of shares at target which could be granted upon vesting of the executive and Business Transformation PSU’s for which performance goals related to 2020 have been established. At December 31, 2020, approximately 224,000 of additional PSUs exist which will vest in tranches based upon achievement of performance goals to be established for fiscal years 2021 and 2022.