NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (in thousands, except for share and per share data)
NOTE 6 — Retirement Plans
We have a number of noncontributory defined benefit pension plans ("pension plans") covering approximately 3% of our active employees. Pension plans covering salaried employees provide pension benefits that are based on the employees´ years of service and compensation prior to retirement. Pension plans covering hourly employees generally provide benefits of stated amounts for each year of service.
We also provide post-retirement life insurance benefits for certain retired employees. Domestic employees who were hired prior to 1982 and certain former union employees are eligible for life insurance benefits upon retirement. We fund life insurance benefits through term life insurance policies and intend to continue funding all of the premiums on a pay-as-you-go basis.
We recognize the funded status of a benefit plan in our consolidated balance sheets. The funded status is measured as the difference between plan assets at fair value and the projected benefit obligation. We also recognize, as a component of other comprehensive earnings, net of tax, the gains or losses and prior service costs or credits that arise during the period but are not recognized as components of net periodic benefit/cost.
The measurement dates for the pension plans for our U.S. and non-U.S. locations were December 31, 2019, and 2018.
During 2017, we offered certain former vested employees in our U.S. pension plan a one-time option to receive a lump sum distribution of their benefits from pension plan assets. The pension plan made approximately $23,912 in lump sum payments to settle its obligation to these participants. These settlement payments decreased the projected benefit obligation and plan assets by $23,912, and resulted in a non-cash settlement charge of $13,476 related to unrecognized net actuarial losses that were previously included in accumulated other comprehensive loss. The measurement date of this settlement was December 31, 2017.
In February 2020, the CTS Board of Directors authorized and empowered management to explore termination of our U.S. based pension plans at management's discretion, subject to certain conditions. Management has not yet made a final decision on whether to pursue a plan termination and the potential timing thereof.
The measurement dates for the post-retirement life insurance plan were December 31, 2019, and 2018. The following table provides a reconciliation of benefit obligation, plan assets, and the funded status of the post-retirement life insurance plan at those measurement dates.

Post-Retirement Life Insurance Plan
2019
2018
Accumulated benefit obligation
$4,766
$4,595
Change in projected benefit obligation:
Projected benefit obligation at January 1
$4,595
$5,134
Service cost
1
2
Interest cost
170
156
Benefits paid
(145)
(157)
Actuarial loss (gain)
145
(540)
Projected benefit obligation at December 31
$4,766
$4,595
Change in plan assets:
Assets at fair value at January 1
$—
$—
Actual return on assets
—
—
Company contributions
145
157
Benefits paid
(145)
(157)
Other
—
—
Assets at fair value at December 31
$—
$—
Funded status (plan assets less projected benefit obligations)
$(4,766)
$(4,595)


Question: Analyse this data from a financial earnings document. What was the change in the Projected benefit obligation at January 1 between 2018 and 2019?
Choices:
0
-539
539
4593
-5128
Correct choice index: 1