257 future benefit obligations within the constraints of a prudent level of portfolio risk and diversification. Aegon believes that the asset  allocation is an important factor in determining the long-term performance of the plan. The plan uses multiple asset classes as well as  sub-classes to meet the asset allocation and other requirements of the investment policy, which minimizes investment risk. From time  to time the actual asset allocation may deviate from the desired asset allocation ranges due to different market performance among  the various asset categories. If it is determined that rebalancing is required, future additions and withdrawals will be used to bring  the allocation to the desired level. Aegon USA maintains minimum required funding levels as set forth by the Internal Revenue Code. If contributions are required,  the funding would be provided from the Company’s general account assets. Pension plan contributions were not required for Aegon  USA in 2013 or 2012. Aegon USA also sponsors supplemental retirement plans to provide senior management with benefits in excess of normal retirement  benefits. The plans are unfunded and are not qualified under the Internal Revenue Code. The supplemental retirement plans are  governed by either Aegon USA, LLC, or the Compensation Committee of the Board of Directors of Aegon US Holding Corporation.  Aegon USA, LLC, or the Compensation Committee of the Board of Directors has the full power and discretion to apply all of the plan’s  provisions, including such responsibilities as, but not limited to, interpret the plan provisions, to make factual determinations under  the plan, to determine plan benefits, and to comply with any statutory reporting and disclosure requirements. The benefits are  based on years of service and the employee’s eligible annual compensation. The plans provide benefits based on a traditional final  average formula or a cash balance formula (which defines the accrued benefit in terms of a stated account balance), depending on  the age and service of the plan participant. The Company funds the benefit payments of the supplemental retirement plans from its  general account assets. The unfunded amount related to these plans, for which a liability has been recorded, was EUR 192 million  (2012: EUR 208 million). Aegon USA provides health care benefits to retired employees, which are unfunded plans. The post-retirement health care plans  are administered by Aegon USA, LLC, which has delegated the claims administration to third party administrators. Aegon USA, LLC  (“Company”) maintains two plans which provide retiree medical benefits. For each plan, the Company has the fiduciary responsibility  to administer the plan in accordance with its terms, and decides questions related to eligibility and determines plan provisions and  benefit amounts. Under the Employee Retirement Income Security Act (ERISA), the Company has the fiduciary responsibility to monitor  the third party claims administrator to ensure it is doing its job properly and to remove the third party administrator if it is not properly  doing its job. In addition, the Company has the fiduciary obligation to interpret the provisions of the plans, and to comply with any  statutory reporting and disclosure requirements. Finally, the Company reviews the terms of the plans and make changes to the plans  if and when appropriate. The Company funds the benefit payments of the post-retirement health care plans from its general account  assets. The post-retirement health benefit liability amounted to EUR 191 million (2012: EUR 198 million). The weighted average duration of the defined benefit obligation is 12.7 years (2012: 14.2 years). The principal actuarial assumptions that apply for the year ended December 31 are as follows: Actuarial assumptions used to determine defined benefit obligations at year­end 2013 2012 Demographic actuarial assumptions Mortality 2014 static  mortality table  1) 2013 static  mortality table  1) Financial actuarial assumptions Discount rate 4.75% 4.00% Salary increase rate 3.91% 3.91% Health care trend rate 8.50% 7.25% 1  Table in accordance with IRS regulation 1.430(h)(3)-1.