The Company contributes to a multiemployer defined benefit pension plan under the terms of a collective-bargaining agreement that covers union-represented employees.

The Company has an unfunded postretirement healthcare plan which provides health insurance to certain retired employees and their spouses. This plan has been frozen, no current employees participate and no additional participants will be added to the plan in the future.


	2023		2022		2021
401(k) plan	$	3,804	$	3,580	$	3,196
Multiemployer and other defined benefit and pension plans	92		79		78
Postretirement healthcare plan	251		342		411
Total retirement plan expense	$	4,147	$	4,001	$	3,685

The Company's one multiemployer plan is underfunded and has a rehabilitation plan in place. The rehabilitation plan requires minimum contributions from the Company. Given the status of this plan, it is reasonably possible that future contributions to the plan will increase although the Company cannot reasonably estimate a possible range of increased contributions as of December 31, 2023.

The following table presents the changes in the accumulated postretirement benefit obligation related to the Company’s unfunded postretirement healthcare benefits at December 31 (in thousands):


	2023		2022
Projected benefit obligation at January 1	$	4,229	$	6,202

Interest cost	194		127


Actuarial loss (gain)	59		(1,784)
Benefits paid, net of contributions	(274)		(316)
Projected benefit obligation at December 31	4,208		4,229
Fair value of plan assets	—		—
Under funded status	(4,208)		(4,229)
Unamortized prior service cost	292		352
Unrecognized actuarial (gain)	(219)		(278)
Net amount recognized	$	(4,135)	$	(4,155)


	2023		2022
Accrued postretirement benefit liability:
Current portion	$	357	$	353
Long term portion	3,851		3,876
Pre-tax accumulated other comprehensive loss – unamortized post-retirement healthcare costs	(73)		(74)
Net amount recognized	$	4,135	$	4,155

Components of net periodic postretirement benefit cost charged to expense for the years ended December 31 were as follows (in thousands):


	2023			2022			2021

Interest cost	$	194		$	127		$	125
Amortization of unrecognized prior service cost	60			60			44
Loss amortization (2)	—			24			113
Net periodic benefit cost	$	254		$	211		$	282
Assumptions used to calculate the benefit obligation:
Discount rate	4.7		%	4.8		%	2.4		%
Annual rate of increase in the per capita cost of:
Medical costs before age 65 (1)	7.8		%	7.8		%	7.0		%
Medical costs after age 65 (1)	4.6		%	4.5		%	4.5		%
Prescription drug costs (1)	7.8		%	7.8		%	7.0		%

(1) For 2023 and 2022, it was assumed that these rates would gradually decline to 4.0% by 2075. For 2021, it was assumed that these rates would gradually decline to 3.8% by 2075.

(2) Actuarial losses are amortized utilizing the corridor approach. Differences between actual experience and the actuarial assumptions are reflected in (gain)/loss. If the total net (gain) or loss exceeds 10 percent of the greater of the accumulated postretirement benefit obligation or plan assets, this excess must be amortized over the average remaining service period of the active plan participants. If most of the plan participants are inactive, the amortization period is the expected future lifetime of inactive plan participants.