Greece
Greek labor legislation requires that the payment of retirement and termination indemnities is based on the number of years of service to the Company by the employees and on their final remuneration. The Group grants retirement indemnities which exceed the legal requirements. These retirement indemnities are unfunded and the liabilities arising from such obligations are actuarially valued by an independent firm of actuaries. The last actuarial valuation was undertaken in December 2016. The principal actuarial assumptions used were a discount rate of 1.5% (2015: 1.9%), future salary increases of 1.75% (2015: 2%) and no change in future pensions.
USA
The Group's U.S. subsidiaries operate defined benefit plans and other post-retirement benefit plans. The method of accounting for the latter, as well as the valuation assumptions and the frequency of valuations are similar to those used for defined benefit plans.
All of the Group's U.S. subsidiaries' defined benefit pension plans and all but one of its other post-retirement plans have been frozen as to new participants and credited service. One post-retirement benefit plan exists (for certain active and former employees) whereby eligible retirees receive benefits consisting primarily of assistance with medical insurance costs between the dates of early retirement and Medicare eligibility.
On 31 December 2016 the plan assets of the Group's subsidiaries in the US have invested approximately 58% (2015: 57%) in equity instruments quated in US and international stock markets and 42% (2015: 43%) in fixed investments (US and international bonds). The discount rate that has been adopted for the study of the pension plans of the Group's subsidiaries in the U.S. was 4% (2015: 4%).
Multi-employer plan
Certain employees participate in a union sponsored, defined benefit multi-employer pension plan. This plan is not administered by the Group's U.S. subsidiaries and contributions are determined in accordance with the provisions of the negotiated labor contract. These contributions are affected by the funded status of the plan.
Excess benefit plan
This plan is intended to constitute an unfunded plan of deferred compensation for a selected group of highly compensated employees under the Employee Income Security Act of 1974 ("ERISA"). For this purpose the Group's U.S. subsidiary created an irrevocable trust to facilitate the payment of deferred compensation to participants under this plan. Under this plan the participants are eligible to defer from 0% to 20% of eligible compensation for the applicable plan year. In 2012, the Group's U.S. subsidiary suspended its matching amounts for all contributions. On 31 December 2016 and 2015, plan assets totaled €4,364 thousand and €4,578 thousands, respectively, and are classified as other non current assets in the accompanying consolidated statement of financial position (note 17). There were no costs for the plan for the year ended 31 December 2016 or 2015.