. in addition , the plan was amended september 1 , 2004 , to provide that ppg management will determine the extent to which future increases in the cost of its retiree medical and prescription drug programs will be shared by certain retirees . the federal subsidy related to providing a retiree prescription drug benefit is not subject to u.s . federal income tax and is recorded as a reduction in annual net periodic benefit cost of other postretirement benefits . in august 2007 , the company 2019s u.s