We maintain the LTIP for certain employees and officers of MGP and its affiliates who perform services for us. The LTIP awards are grants of non-vested "phantom" or notional units, also referred to as "restricted units", which upon

satisfaction of time and performance-based vesting requirements, entitle the LTIP participant to receive ARLP common units. Annual grant levels and vesting provisions for designated participants are recommended by the Chairman, President and CEO of MGP, subject to review and approval of the Compensation Committee. Vesting of all grants outstanding is subject to the satisfaction of certain financial tests, which management currently believes is probable. Grants issued to LTIP participants are expected to cliff vest on January 1st of the third year following issuance of the grants. We account for forfeitures of non-vested LTIP grants as they occur. We expect to settle the non-vested LTIP grants by delivery of ARLP common units, except for the portion of the grants that will satisfy employee tax withholding obligations of LTIP participants. As provided under the distribution equivalent rights ("DERs") provisions of the LTIP and the terms of the LTIP awards, all non-vested grants include contingent rights to receive quarterly distributions in cash or, at the discretion of the Compensation Committee, phantom units in lieu of cash credited to a bookkeeping account with value equal to the cash distributions we make to unitholders during the vesting period.

(1)	During the years ended December 31, 2019, 2018 and 2017, we issued 596,650, 191,858 and 222,011, respectively, unrestricted common units to the LTIP participants. The remaining vested units were settled in cash primarily to satisfy tax withholding obligations of the LTIP participants.

For the years ended December 31, 2019, 2018 and 2017, our LTIP expense was $10.4 million, $10.8 million and $11.0 million, respectively. The total obligation associated with the LTIP as of December 31, 2019 and 2018 was $20.2 million and $20.8 million, respectively, and is included in the partners' capital Limited partners-common unitholders line item in our consolidated balance sheets. As of December 31, 2019, there was $12.5 million in total unrecognized compensation expense related to the non-vested LTIP grants that are expected to vest. That expense is expected to be recognized over a weighted-average period of 1.2 years.

On January 22, 2020, the Compensation Committee determined that the vesting requirements for the 2017 grants of 424,486 restricted units (which was net of 50,824 forfeitures and previously settled units) had been satisfied as of January 1, 2020. As a result of this vesting, on February 10, 2020, we issued 279,622 unrestricted common units to the LTIP participants. The remaining units were settled in cash to satisfy tax withholding obligations of the LTIP participants. On January 22, 2020, the Compensation Committee also authorized additional grants of 965,035 restricted units, of which 950,035 units were granted.

After consideration of the January 1, 2020 vesting and subsequent issuance of 279,622 common units, approximately 1.0 million units remain available under the LTIP for issuance in the future, assuming all grants issued in 2020, 2019 and 2018 and currently outstanding are settled with common units, without reduction for tax withholding, no future forfeitures occur and DERs continue being paid in cash versus additional phantom units.

Supplemental Executive Retirement Plan and Directors' Deferred Compensation Plan

We utilize the SERP to provide deferred compensation benefits for certain officers and key employees. All allocations made to participants under the SERP are made in the form of "phantom" ARLP units and SERP distributions will be settled in the form of ARLP common units. The SERP is administered by the Compensation Committee.

Our directors participate in the Directors' Deferred Compensation Plan. Pursuant to the Directors' Deferred Compensation Plan, for amounts deferred either automatically or at the election of the director, a notional account is established and credited with notional common units of ARLP, described in the Directors' Deferred Compensation Plan as "phantom" units. Distributions from the Directors' Deferred Compensation Plan will be settled in the form of ARLP common units.

For both the SERP and Directors' Deferred Compensation Plan, when quarterly cash distributions are made with respect to ARLP common units, an amount equal to such quarterly distribution is credited to each participant's notional account as additional phantom units. All grants of phantom units under the SERP and Directors' Deferred Compensation Plan vest immediately.

A summary of SERP and Directors' Deferred Compensation Plan activity is as follows:


	Number of units	Weighted average grant date fair value per unit		Intrinsic value
				(in thousands)

Phantom units outstanding as of January 1, 2017	494,018	$	29.77	$	11,091
Granted	67,766		20.38
Phantom units outstanding as of December 31, 2017	561,784		28.64		11,067
Granted	84,417		18.78
Issued (1)	(10,364)		27.92
Phantom units outstanding as of December 31, 2018	635,837		27.34		11,025
Granted	111,012		14.50
Issued (1)	(115,484)		25.20
Phantom units outstanding as of December 31, 2019	631,365		25.48		6,831

(1)	During the years ended December 31, 2019 and 2018, we issued ARLP common units of 115,484 and 7,181, respectively, to participants under the SERP and Directors' Deferred Compensation Plan. Units issued in 2018 were net of units settled in cash to satisfy tax withholding obligations.

Total SERP and Directors' Deferred Compensation Plan expense was $1.6 million, $1.6 million and $1.4 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019 and 2018, the total obligation associated with the SERP and Directors' Deferred Compensation Plan was $16.1 million and $17.4 million, respectively, and is included in the partners' capital Limited partners-common unitholders line item in our consolidated balance sheets.

See Note 2 – Summary of Significant Accounting Policies for more information on our accounting policy for unit-based compensation.