The Company has a 401(k) profit-sharing plan for U.S. employees meeting certain requirements, in which eligible employees may contribute between 1% and 50% of their annual compensation to this plan, and, with respect to employees who are age 50 and older, certain specified additional amounts, limited by an annual maximum amount determined by the Internal Revenue Service. The Company, at its discretion, makes certain matching contributions to this plan based on participating employees’ annual contribution to this plan and their total compensation. The Company’s contributions were $7.6, $7.2 and $6.9 for 2021, 2020 and 2019, respectively.

The Company also has a small number of defined contribution plans at some of its foreign locations. The Company’s contributions were immaterial for 2021, 2020 and 2019.

The Company maintains a bonus plan which provides cash awards to certain employees, at the discretion of the Compensation Committee of the Company’s Board of Directors, based upon the Company’s operating results. In addition, the Company’s foreign locations also have various bonus plans based upon local operating results and employee performance. The total bonus expense was $75.6, $66.4 and $32.2 for 2021, 2020 and 2019, respectively.

The Company provides supplemental retirement benefits for a small number of retired executives. The total cost of these benefits was $0.1, $0.3 and $3.2 for 2021, 2020 and 2019, respectively. The accumulated benefit obligation was $2.6 and $2.5 as of December 31, 2021 and 2020, respectively, and was included in other non-current liabilities.

The Company also assumed deferred compensation plans as a result of the Newport Merger and the ESI Merger. Participants in the Newport Deferred Compensation Plan were not permitted to make any new elections beginning with 2018 compensation. Participants in the ESI Deferred Compensation Plan were not permitted to make any new elections beginning with 2020 compensation.

The Company has a number of defined benefit pension plans, which cover substantially all of its full-time employees in France, Germany, Israel, Japan and Taiwan. In addition, the Company has certain pension assets and liabilities relating to its former employees in the United Kingdom. The German plan is unfunded, as permitted under the plan and applicable laws.

For financial reporting purposes, the Company obtained actuarial reports supporting the calculation of net periodic pension costs that used a number of actuarial assumptions, including a discount rate for plan obligations, an assumed rate of return on pension plan assets and an assumed rate of compensation increase for employees covered by the various plans. The Company reviewed these actuarial assumptions and concluded they were reasonable based upon management’s judgment, considering known trends and uncertainties. Actual results that differ from these assumptions would impact future expense recognition and the cash funding requirements of the Company’s pension plans.

	Year Ended December 31,
	2021			2020
Service cost	$	1.1		$	1.0
Interest cost on projected benefit obligations		0.2			0.4
Expected return on plan assets		(0.1	)		(0.1	)
Amortization of actuarial net loss		0.7			0.5
	$	1.9		$	1.8

The changes in projected benefit obligations and plan assets, as well as the ending balance sheet amounts for the Company’s defined benefit plans, were as follows:

	Year Ended December 31,
	2021			2020
Change in projected benefit obligations:
Projected benefit obligations, beginning of year	$	36.2		$	30.1
Service cost		1.1			1.0
Interest cost		0.2			0.4
Contributions by plan participants		—			0.7
Plan amendments		—			(0.2	)
Actuarial loss		0.1			3.0
Benefits paid		(1.4	)		(1.2	)
Currency translation adjustments		(2.2	)		2.4
Projected benefit obligations, end of year	$	34.0		$	36.2

Change in plan assets:
Fair value of plan assets, beginning of year	$	12.9		$	11.1
Company contributions		0.7			1.1
(Loss) gain on plan assets		(0.1	)		0.6
Benefits paid		(0.6	)		(0.5	)
Currency translation adjustments		(0.6	)		0.6
Fair value of plan assets, end of year		12.3			12.9
Net underfunded status	$	(21.7	)	$	(23.3	)

As of December 31, 2021, the estimated benefit payments for the Company’s defined benefit plans for the next 10 years were as follows:

	Estimated benefit payments
2022	$	1.1
2023		1.1
2024		1.2
2025		1.6
2026		1.4
2027-2031		8.6
	$	15.0

The weighted-average rates used to determine the net periodic benefit costs were as follows:

	December 31, 2021			December 31, 2020
Discount rate		1.0	%		1.1	%
Rate of increase in salary levels		2.0	%		2.2	%
Expected long-term rate of return on assets		1.1	%		1.2	%

In determining the expected long-term rate of return on plan assets, the Company considers the relative weighting of plan assets, the historical performance of total plan assets and individual asset classes, and economic and other indicators of future performance.

Plan assets were held in the following categories as a percentage of total plan assets:

	December 31, 2021					December 31, 2020
	Amount		Percentage			Amount		Percentage
Cash	$	0.2		1.6	%	$	0.2		1.3	%
Debt securities		5.1	41.5				5.2	40.5
Equity securities		0.6	4.8				0.7	5.6
Other		6.4		52.1			6.8	52.6
	$	12.3		100	%	$	12.9		100	%

In general, the Company’s asset management objectives include maintaining an adequate level of diversification to reduce interest rate and market risk, while providing adequate liquidity to meet immediate and future benefit payment requirements.

The Company’s Israeli plans account for the deferred vested benefits using the shut-down method of accounting, which resulted in assets of $20.3 and vested benefit obligations of $23.1 as of December 31, 2021, and assets of $18.8 and vested benefit obligations of $21.7 as of December 31, 2020. Under the shut-down method, the liability is calculated as if it were payable as of the balance sheet date, on an undiscounted basis.

As of December 31, 2021 and 2020, the Company had assets with an aggregate market value of $6.2 and $6.5, respectively, for its German pension plans. These assets are invested in group insurance contracts through the insurance companies administering these plans, in accordance with applicable pension laws. These group insurance contracts have a guaranteed minimum rate of return ranging from 2.25% to 4.25%, depending on the contract. Because these assets were not separate legal assets of the pension plan, they were not included in the Company’s plan assets shown above. However, the Company has designated such assets to pay pension benefits. Such assets are included in other assets in the accompanying consolidated balance sheet.