The Company’s 2016 Incentive Compensation Plan (the “2016 Plan”) was approved by stockholders in May 2016. Under the 2016 Plan, Perdoceo may grant to eligible participants awards of stock options, stock appreciation rights, restricted stock, restricted stock units, deferred stock, performance units, annual incentive awards, and substitute awards, which generally may be settled in cash or shares of our common stock. The vesting of all types of awards is subject to possible acceleration in certain circumstances. If a plan participant terminates employment for any reason other than by death or disability during the vesting period, the right to unvested awards is generally forfeited.

For the quarters ended March 31, 2021 and 2020, the Company granted approximately 0.3 million and 0.2 million restricted stock units, respectively, to be settled in shares of stock which are not “performance-based,” with a grant-date fair value of approximately $3.6 million and $3.5 million, respectively.

Additionally, for the quarters ended March 31, 2021 and 2020, the Company granted approximately 0.4 million and 0.3 million restricted stock units, respectively, to be settled in shares of stock which are “performance-based,” with a grant-date fair value of approximately $4.2 million and $3.9 million, respectively. The performance-based restricted stock units are subject to performance conditions which are determined at the time of grant and typically cover a three-year performance period. These performance conditions may result in all units being forfeited even if the requisite service period is met.

There were no stock options granted during each of the quarters ended March 31, 2021 and 2020.

Total share-based compensation expense for the quarters ended March 31, 2021 and 2020 for all types of awards was as follows (dollars in thousands):

	For the Quarter Ended March 31,
Award Type	2021		2020
Stock options	$	160	$	405
Restricted stock units settled in stock		3,588		2,803
Restricted stock units settled in cash		-		(240	)
Total share-based compensation expense	$	3,748	$	2,968

As of March 31, 2021, we estimate that compensation expense of approximately $23.0 million will be recognized over the next four years for all unvested share-based awards that have been granted to participants. This amount excludes any estimates of forfeitures.