We have stock option and stock incentive plans for employees and non-employee Directors that provide for grants of restricted stock awards (“RSAs”), restricted stock units (“RSUs”), performance stock units (“PSUs”), and options to purchase shares of our common stock at exercise prices generally equal to the fair value of such stock at the dates of grant. We also maintain a shareholder-approved Employee Stock Purchase Plan (“ESPP”) for the benefit of our employees. The ESPP allows eligible employees to purchase common stock on a regular basis at the lower of 85% of the market price at the beginning or end of each offering period.

During the nine months ended September 30, 2021 the Compensation Committee of our Board of Directors (the “Committee”) authorized awards from approved stock incentive plans of RSUs to certain employees, RSAs to non-employee Directors, and RSAs and PSUs to certain Company officers, which, assuming that performance under the PSUs were to be achieved at target levels, together totaled 494,000 shares and had an aggregate grant date market value of $12.5 million.

During the nine months ended September 30, 2020 the Committee authorized awards from approved stock incentive plans of RSUs to certain employees, RSAs to non-employee Directors, and RSAs and PSUs to certain Company officers, which, assuming that performance under the PSUs were to be achieved at target levels, together totaled 330,000 shares and had an aggregate grant date market value of $8.2 million. In February 2021, the Committee used structured discretion to determine that the 2020 PSUs were earned and should be paid out at 100% of target resulting in a modification of the award which resulted in $1.2 million of compensation expense during the nine months ended September 30, 2021 related to these performance awards.

The Committee authorized, from approved stock incentive plans, grants of stock options to purchase a total of 226,000 and 212,000 shares to certain Company officers during the nine months ended September 30, 2021 and 2020, respectively. The exercise prices of the options were equal to the closing stock prices on their respective grant dates.

Employees purchased common stock totaling 51,000 and 87,000 shares in the three and nine months ended September 31, 2021, respectively, as compared to 54,000 and 84,000 shares in the three and nine months ended September 30, 2020, respectively, through the ESPP.

Stock Compensation Expense

The following weighted-average assumptions were used to determine the fair value of options and shares purchased under the ESPP:


	Three Months Ended		Nine Months Ended
	September 30, 2021		September 30, 2021
	Stock Options	ESPP	Stock Options	ESPP
Expected life	N/A	0.5 Years	5.0 Years	0.5 Years
Expected stock price volatility	N/A	0.44	0.40	0.46
Risk-free interest rate	N/A	0.05%	0.57%	0.09%

The following table summarizes total stock compensation expenses prior to the capitalization of amounts into Deferred preservation and Inventory costs (in thousands):


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
RSA, RSU, and PSU expense	$	2,465	$	1,984	$	6,211	$	6,189
Stock option and ESPP expense		525		534		1,684		1,699
Total stock compensation expense	$	2,990	$	2,518	$	7,895	$	7,888

Included in the total stock compensation expense, as applicable in each period, were expenses related to RSAs, RSUs, PSUs, and stock options issued in each respective year, as well as those issued in prior periods that continue to vest during the period, and compensation related to the ESPP. These amounts were recorded as stock compensation expense and were subject to our normal allocation of expenses to inventory costs and deferred preservation costs. We capitalized $115,000 and $424,000 in the three and nine months ended September 30, 2021, respectively, and $160,000 and $456,000 in the three and nine months ended September 30, 2020, respectively, of the stock compensation expense into our inventory costs and deferred preservation costs.

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