The table below sets forth information related to our share-based compensation expense:


	Three Months Ended
	March 31,
	2023		2022
Cost of goods sold	$	452	$	347
Selling, general and administrative		8,362		6,534
Research and development		1,006		1,021
Total share-based compensation expense	$	9,820	$	7,902

Share Grants – Share grants consist of restricted stock awards, restricted stock units and performance stock units ("PSUs"). Restricted stock awards and restricted stock units generally vest in equal annual installments over a four-year period and are measured based on the fair market value of the underlying stock on the date of grant. Compensation expense is recognized on a straight-line basis over the requisite four-year service period. All new grants are granted under the Company’s 2022 Equity Incentive Plan.

Performance stock units (“PSUs”) are measured based on the fair market value of the underlying stock on the date of grant, and compensation expense is recognized over the three-year performance period, with adjustments made to the expense to recognize the probable payout percentage.

As of March 31, 2023, total unrecognized share-based compensation expense related to share grants was approximately $66.5 million, before income taxes, and is expected to be recognized over a weighted average period of approximately 2.3 years.

Stock Modification. During the three months ended March 31, 2023 we modified previously granted stock awards for two corporate officers who retired. The result of the modification was the acceleration of the vesting of 54,525 stock awards for the corporate officers. The incremental expense recorded for this modification was approximately $2.1 million, which was expensed in SG&A in the three months ended March 31, 2023.