We maintain single-employer noncontributory defined benefit pension plans covering certain employees. There have been no new entrants to the U. S. Silica Company plan since May 2009 and to the EP Management Corporation plan since January 2007 for salaried participants and January 2010 for hourly participants when the plans were frozen to all new employees. The plans provide benefits based on each covered employee’s years of qualifying service. Our funding policy is to contribute amounts within the range of the minimum required and maximum deductible contributions for the plans consistent with a goal of appropriate minimization of the unfunded projected benefit obligations. The pension plans use a benefit level per year of service for covered hourly employees and a final average pay method for covered salaried employees. The plans use the projected unit credit cost method to determine the actuarial valuation.

We employ a total rate of return investment approach whereby a mix of equities and fixed income investments are used to maximize the long-term return of plan assets for a prudent level of risk. Risk tolerance is established through careful consideration of plan liabilities, plan funded status, and corporate financial condition. The investment portfolio contains a diversified blend of equity and fixed-income investments. Furthermore, equity investments are diversified across U.S. and non-U.S. stocks, as well as growth, value and small and large capitalizations. Investment risk is measured and monitored on an ongoing basis through quarterly investment portfolio reviews, annual liability measurements, and periodic asset/liability studies.

We employ a building block approach in determining the long-term rate of return for plan assets. Historical markets are studied and long-term historical relationships between equities and fixed-income are preserved consistent with the widely accepted capital market principle that assets with higher volatility generate a greater return over the long run. Current market factors such as inflation and interest rates are evaluated before long-term capital market assumptions are determined. The long-term portfolio return is established via a building block approach with proper consideration of diversification and rebalancing. Peer data and historical returns are reviewed to check for reasonability and appropriateness.

In addition, we provide defined benefit post-retirement health care and life insurance benefits to some employees. Covered employees become eligible for these benefits at retirement after meeting minimum age and service requirements. The projected future cost of providing post-retirement benefits, such as healthcare and life insurance, is recognized as an expense as employees render services. We previously maintained a Voluntary Employees’ Beneficiary Association trust that was used to partially fund health care benefits for future retirees. Benefits were funded to the extent contributions were tax deductible, which under current legislation is limited. In 2017, the trust terminated upon depletion of its assets, which were used in accordance with trust terms. In general, retiree health benefits are paid as covered expenses are incurred.



	Year Ended December 31,
	2019			2018			2017
Service cost	$	1,304		$	1,307		$	1,037
Interest cost	5,375			4,632			3,971
Expected return on plan assets	(6,171		)	(5,969		)	(5,265		)
Net amortization and deferral	1,648			2,526			1,773
Net pension benefit costs	$	2,156		$	2,496		$	1,516



	Year Ended December 31,
	2019			2018		2017
Service cost	$	88		$	102	$	107
Interest cost	789			740		753
Expected return on plan assets	—			—		(1		)
Unrecognized net (gain)/loss	(29		)	—		—
Net post-retirement benefit costs	$	848		$	842	$	859



	Pension Benefits						Post-retirement Benefits
	2019			2018			2019			2018
Benefit obligation at January 1,	$	138,900		$	122,052		$	21,570		$	22,771
Service cost	1,304			1,307			88			102
Interest cost	5,375			4,632			789			740
Actuarial (gain) loss	17,225			(10,263		)	206			(965		)
Benefits paid	(14,922		)	(8,202		)	(815		)	(1,499		)
Other⁽¹⁾	609			29,374			216			421
Benefit obligation at December 31,	$	148,491		$	138,900		$	22,054		$	21,570
Fair value of plan assets at January 1,	$	102,396		$	92,067		$	—		$	—
Actual return on plan assets	17,919			(6,204		)	—			—
Employer contributions	4,755			3,350			599			1,078
Benefits paid	(14,922		)	(8,202		)	(815		)	(1,499		)
Other⁽¹⁾	283			21,385			216			421
Fair value of plan assets at December 31,	$	110,431		$	102,396		$	—		$	—
Plan assets less than benefit obligations at December 31 recognized as liability for pension and other post-retirement benefits	$	(38,060	)	$	(36,504	)	$	(22,054	)	$	(21,570	)



(1	)	Includes opening pension benefit obligation and plan assets balances related to the May 1, 2018, EPMH acquisition and other adjustments.

We also sponsor unfunded, nonqualified pension plans. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans were $1.6 million, $1.6 million and zero, respectively, at December 31, 2019 and $1.5 million, $1.5 million and zero. respectively, at December 31, 2018.



	Benefits
			Post-retirement
	Pension		Before Medicare Subsidy		After Medicare Subsidy
2020	$	10,025	$	1,601	$	1,431
2021	9,221		1,669		1,502
2022	9,195		1,686		1,520
2023	9,208		1,659		1,492
2024	9,551		1,677		1,513
2025-2029	45,386		7,526		6,677

The total amounts in accumulated other comprehensive income (loss) related to net actuarial loss, net of tax, for the pension and post-retirement plans was $22.1 million and $17.6 million as of December 31, 2019 and 2018, respectively. The total amounts in accumulated other comprehensive income (loss) related to prior service cost, net of tax, for the pension and post-retirement plans, was $2.2 million and $2.8 million as of December 31, 2019 and 2018, respectively.



	Pension Benefits				Post-retirement Benefits
	2019		2018		2019		2018
Discount rate	3.2	%	4.4	%	3.2	%	4.3	%
Long-term rate of compensation increase	3.0%-3.5%		3.0%-3.5%		N/A		N/A
Long-term rate of return on plan assets	6.3	%	6.25%-7.15%		N/A		N/A
Health care cost trend rate:
Pre-65 initial rate/ultimate rate	N/A		N/A		7.0%/4.5%		7.3%/4.5%
Pre-65 ultimate year	N/A		N/A		—		—
Post-65 initial rate/ultimate rate	N/A		N/A		7.5%/4.5%		8.0%/4.5%
Post-65 ultimate year	N/A		N/A		2026/2027		2026/2027

The weighted average discount rate used to determine the projected pension and post-retirement obligations was updated to 3.2% at December 31, 2019 from 4.4% at December 31, 2018. The discount rate reflects the expected long-term rates of return with maturities comparable to payments for the plan obligations utilizing Aon Hewitt's AA Above Medium Curve.

Mortality tables used for pension benefits and post-retirement benefits plans are the following:



	Pension and Post-retirement Benefits
	2019	2018
Healthy Lives	Pri-2012 base mortality tables with generational mortality improvements using Scale MP-2019	RP-2014 mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2018
Disabled Lives	Pri-2012 base mortality tables with generational mortality improvements using Scale MP-2019	RP-2014 disabled retiree mortality table, adjusted back to 2006 base rates, with generational mortality improvements using Scale MP-2018

Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effects (in thousands):



	One-Percentage-Point
	Increase		Decrease
Effect on total of service and interest cost	$	100	$	(85	)
Effect on post-retirement benefit obligation	2,341		(2,010		)



	Pension Benefits				Post-retirement Benefits⁽¹⁾
	2019		2018		2019		2018
Equity securities	52.1	%	42.1	%	—	%	—	%
Debt securities	46.6	%	55.5	%	—	%	—	%
Cash	1.3	%	2.4	%	—	%	—	%



(1	)	Retiree health benefits are paid by the Company as covered expenses are incurred.



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	—	$	1,385	$	—	$	1,385
Mutual funds:
Diversified emerging markets	4,942		—		—		4,942
Foreign large blend	19,183		—		—		19,183
Large-cap blend	20,738		—		—		20,738
Mid-cap blend	8,416		—		—		8,416
Real estate	4,309		—		—		4,309
Fixed income securities:
Corporate notes and bonds	37,664		—		—		37,664
U.S. Treasuries	10,894		—		—		10,894
Mortgage-backed securities	—		2,496		—		2,496
Asset-backed securities	—		404		—		404
Net asset	$	106,146	$	4,285	$	—	$	110,431

The fair values of the pension plan assets (in thousands) at December 31, 2018, by asset category, are as follows:



	Level 1		Level 2		Level 3		Total
Cash and cash equivalents	$	—	$	2,449	$	—	$	2,449
Mutual funds:
Diversified emerging markets	6,638		—		—		6,638
Foreign large blend	11,689		—		—		11,689
Large-cap blend	14,226		—		—		14,226
Mid-cap blend	6,819		—		—		6,819
Small-cap blend	522		—		—		522
Real estate	3,192		—		—		3,192
Fixed income securities:
Corporate notes and bonds	43,745		—		—		43,745
U.S. Treasuries	8,486		—		—		8,486
Mortgage-backed securities	—		3,578		—		3,578
Asset-backed securities	—		1,052		—		1,052
Net asset	$	95,317	$	7,079	$	—	$	102,396

We contribute to three multiemployer defined benefit pension plans under the terms of collective-bargaining agreements for union-represented employees. A multiemployer plan is subject to collective bargaining for employees of two or more unrelated companies. These plans allow multiple employers to pool their pension resources and realize efficiencies associated with the daily administration of the plan. Multiemployer plans are generally governed by a board of trustees composed of management and labor representatives and are funded through employer contributions. However, in most cases, management is not directly represented.

The risks of participating in multiemployer plans differ from single employer plans as follows: 1) assets contributed to a multiemployer plan by one employer may be used to provide benefits to employees of other participating employers, 2) if a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers, and 3) if we cease to have an obligation to contribute to one or more of the multiemployer plans to which we contribute, we may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability.

A summary of each multiemployer pension plan for which we participate is presented below:

Pension

Fund

EIN/ Pension

Plan No.

Pension Protection Act

Zone Status⁽¹⁾

FIP/RP Status

Pending/

Implemented

Company

Contributions

(in thousands)

Surcharge

Imposed

Expiration

Date of

CBA

2019

2018

2019

2018

2017

LIUNA

52-6074345/001

Red

Yes

385

573

223

Yes

5/31/2020

IUOE

36-6052390/001

Green

310

1,385

7/31/2022

CSSS⁽²⁾

36-6044243/001

Red

Yes

Our contributions to individual multiemployer pension funds did not exceed 5% of the fund’s total contributions for the years ended December 31, 2019, 2018 and 2017. Additionally, our contributions to multiemployer post-retirement benefit plans were immaterial for all periods presented in the accompanying consolidated financial statements.

We also sponsor a defined contribution plan covering certain employees. We contribute to the plan in two ways. For certain employees not covered by the defined benefit plan, we make a contribution equal to 4% of their salary. We may also contribute an employee discretionary match of up to 50 cents for each dollar contributed by an employee, up to 4% of their earnings. Finally, for some employees, we make a catch-up match of one dollar for each dollar contributed by an employee, up to 6% of catch-up contributions. Contributions were $6.1 million, $2.6 million and $3.0 million for the years ended December 31, 2019, 2018 and 2017, respectively.