The Company maintains a qualified defined contribution 401(k) plan covering substantially all of its employees in the U.S. The Company may, at its discretion, make contributions to the plan. The Company recorded expense of $4.1 million, $3.5 million, and $0.2 million related to the 401(k) plan for the years ended December 31, 2019, 2018 and 2017, respectively.

As part of the acquisition of Partnerships in Care on July 1, 2014, the Company assumed a frozen contributory defined benefit retirement plan (“Partnerships in Care Pension Plan”) covering substantially all of the employees of Partnerships in Care and its subsidiaries prior to May 1, 2005 at which time, the Partnerships in Care Plan was frozen to new participants. Effective May 2015, the active participants no longer accrue benefits. The benefits under the Partnerships in Care Pension Plan were primarily based on years of service and final average earnings.

The Company accounts for the Partnerships in Care Pension Plan in accordance with ASC 715-30 “Compensation — Defined Benefit Plans”, (“ASC 715-30”). In accordance with ASC 715-30, the Company recognizes the unfunded liability of the Partnerships in Care Pension Plan on the Company’s consolidated balance sheet and unrecognized gains (losses) and prior service credits (costs) as changes in other comprehensive income (loss). The measurement date of the Partnerships in Care Pension Plan’s assets and liabilities coincides with the Company’s year-end. The Company’s pension benefit obligation is measured using actuarial calculations that incorporate discount rates, rate of compensation increases, when applicable, expected long-term returns on plan assets and consider expected age of retirement and mortality. Expected return on plan assets is determined by using the specific asset distribution at the measurement date.

The following table summarizes the funded status (unfunded liability) of the Partnerships in Care Pension Plan based upon actuarial valuations prepared at December 31, 2019 and 2018 (in thousands):

	2019		2018
Projected benefit obligation	$	66,468	$	57,993
Fair value of plan assets		62,207		54,491
Unfunded liability	$	4,261	$	3,502

The following table summarizes changes in the Partnerships in Care Pension Plan net pension liability at December 31, 2019 and 2018 (in thousands):

	2019			2018
Net pension liability at beginning of period	$	3,502		$	8,795
Employer contributions		(2,413	)		(2,267	)
Net pension expense		(933	)		283
Pension liability adjustment		4,012			(2,803	)
Foreign currency translation (loss) gain		93			(506	)
Net pension liability at end of period	$	4,261		$	3,502

A pension liability of $4.3 million and $3.5 million were recorded within other liabilities on the consolidated balance sheets at December 31, 2019 and 2018. The following assumptions were used to determine the plan benefit obligation:

Discount rate		1.9	%		2.8	%
Compensation increase rate		2.9	%		3.3	%
Measurement date	December 31, 2019			December 31, 2018

A summary of the components of net pension plan expense for the years ended December 31, 2019 and 2018 is as follows (in thousands):

	2019			2018
Interest cost on projected benefit obligation	$	1,605		$	1,602
Expected return on assets		(2,538	)		(1,319	)
Net pension expense	$	(933	)	$	283

Assumptions used to determine the net periodic pension plan expense for the years ended December 31, 2019 and 2018 were as follows:

	2019			2018
Discount rate		1.9	%		2.8	%
Expected long-term rate of return on plan assets		1.9	%		2.8	%

The Company recognizes changes in the funded status of the pension plan as a direct increase or decrease to stockholders’ equity through accumulated other comprehensive income. The accumulated other comprehensive income (loss) related to the Partnerships in Care Pension Plan, net of taxes, for the years ended December 31, 2019, 2018 and 2017 was $(5.2) million, $(1.8) million and $(4.5) million, respectively.

The trustees of the Partnerships in Care Pension Plan are required to invest assets in the best interest of the Partnerships in Care Pension Plan’s members and also ensure liquid assets are available to make benefit payments as they become due. Performance of the Partnerships in Care Pension Plan’s assets are monitored quarterly, at a minimum, and asset allocations are adjusted as needed. The Partnerships in Care Pension Plan’s weighted-average asset allocations by asset category at December 31, 2019 and 2018 were as follows:

	December 31, 2019			December 31, 2018
Cash and cash equivalents		1.4	%		1.3	%
U.K. government obligation		16.2	%		15.0	%
Annuity contracts		35.1	%		38.6	%
Equity securities		28.8	%		25.4	%
Debt securities		12.5	%		15.8	%
Other		6.0	%		3.9	%

At December 31, 2019 and 2018, the Partnerships in Care Pension Plan cash and cash equivalents were classified as Level 1 in the GAAP fair value hierarchy. Fair values were based on utilizing quoted prices (unadjusted) in active markets for identical assets. The U.K. government obligations, annuity contracts, equity securities, debt securities and other investments were classified as Level 2 in the GAAP fair value hierarchy. Fair values were based on data points that are observable, such as quoted prices, interest rates and yield curves.