balance at december 31 $ 99 $ 110 the amount of unrecognized tax benefits was $ 99 million and $ 110 million as of december 31 , 2008 and 2007 , respectively . if recognized , $ 89 million and $ 88 million would impact the effective rate as of december 31 , 2008 and 2007 , respectively . the company recognizes accrued interest and penalties related to unrecognized tax benefits in income tax expense . the company had accrued $ 10 million and $ 9 million for estimated interest and penalties on unrecognized tax benefits as of december 31 , 2008 and 2007 , respectively . the company recognized $ 1 million and $ 3 million of expense for estimated interest and penalties during the years ended december 31 , 2008 and 2007 , respectively . while it is expected that the amount of unrecognized tax benefits will change in the next 12 months , quantification of an estimated range cannot be made at this time . the company does not expect this change to have a significant impact on the results of operations or financial position of the company , however , actual settlements may differ from amounts accrued . 14 . pensions and other postretirement benefits defined benefit plans ppg has defined benefit pension plans that cover certain employees worldwide . ppg also sponsors welfare benefit plans that provide postretirement medical and life insurance benefits for certain u.s . and canadian employees and their dependents . these programs require retiree contributions based on retiree-selected coverage levels for certain retirees and their dependents and provide for sharing of future benefit cost increases between ppg and participants based on management discretion . the company has the right to modify or terminate certain of these benefit plans in the future . salaried and certain hourly employees hired on or after october 1 , 2004 , are not eligible for postretirement medical benefits . salaried employees hired , rehired or transferred to salaried status on or after january 1 , 2006 , and certain hourly employees hired in 2006 or thereafter are eligible to participate in a defined contribution retirement plan . these employees are not eligible for defined benefit pension plan benefits . the medicare act of 2003 introduced a prescription drug benefit under medicare ( 201cmedicare part d 201d ) that provides several options for medicare eligible participants and employers , including a federal subsidy payable to companies that elect to provide a retiree prescription drug benefit which is at least actuarially equivalent to medicare part d . during the third quarter of 2004 , ppg concluded its evaluation of the provisions of the medicare act and decided to maintain its retiree prescription drug program and to take the subsidy available under the medicare act . the impact of the medicare act was accounted for in accordance with fasb staff position no . 106-2 , 201caccounting and disclosure requirements related to the medicare prescription drug , improvement and modernization act of 2003 201d effective january 1 , 2004 . 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 . other postretirement benefit plan was amended to consolidate the number of retiree health care options available for certain retirees and their dependents . the plan amendment was effective january 1 , 2008 . the amended plan also offers a fully-insured medicare part d prescription drug plan for certain retirees and their dependents . as such , beginning in 2008 ppg is no longer eligible to receive the subsidy provided under the medicare act of 2003 for these retirees and their dependents . the impact of the plan amendment was to reduce the accumulated plan benefit obligation by $ 57 million . 50 2008 ppg annual report and form 10-k .
notes to the consolidated financial statements the activity in the accrued liability for unrecognized tax benefits for the two years ended december 31 , 2008 was as follows : ( millions ) 2008 2007 .
what was the percentage net change in the accrued liability for unrecognized tax benefits from 2007 to 2008?
( millions ) the balance at december 31 of 2008 is $ 99 ; the balance at december 31 of 2007 is $ 110 ;
( millions ) 2008 2007
balance at january 1 $ 110 $ 77
additions based on tax positions related to the current year 12 21
additions for tax positions of prior years 5 19
reductions for tax positions of prior years -17 ( 17 ) -5 ( 5 )
pre-acquisition unrecognized tax benefits 20 2014
reductions for expiration of the applicable statute of limitations -6 ( 6 ) -5 ( 5 )
settlements -21 ( 21 ) -1 ( 1 )
currency -4 ( 4 ) 4
balance at december 31 $ 99 $ 110