as of december 31 , 2017 , the company had gross state income tax credit carry-forwards of approximately $ 20 million , which expire from 2018 through 2020 .a deferred tax asset of approximately $ 16 million ( net of federal benefit ) has been established related to these state income tax credit carry-forwards , with a valuation allowance of $ 7 million against such deferred tax asset as of december 31 , 2017 .the company had a gross state net operating loss carry-forward of $ 39 million , which expires in 2027 .a deferred tax asset of approximately $ 3 million ( net of federal benefit ) has been established for the net operating loss carry-forward , with a full valuation allowance as of december 31 , 2017 .other state and foreign net operating loss carry-forwards are separately and cumulatively immaterial to the company 2019s deferred tax balances and expire between 2026 and 2036 .14 .debt long-term debt consisted of the following: .
[['( $ in millions )', 'december 31 2017', 'december 31 2016'], ['senior notes due december 15 2021 5.000% ( 5.000 % )', '2014', '600'], ['senior notes due november 15 2025 5.000% ( 5.000 % )', '600', '600'], ['senior notes due december 1 2027 3.483% ( 3.483 % )', '600', '2014'], ['mississippi economic development revenue bonds due may 1 2024 7.81% ( 7.81 % )', '84', '84'], ['gulf opportunity zone industrial development revenue bonds due december 1 2028 4.55% ( 4.55 % )', '21', '21'], ['less unamortized debt issuance costs', '-26 ( 26 )', '-27 ( 27 )'], ['total long-term debt', '1279', '1278']]
credit facility - in november 2017 , the company terminated its second amended and restated credit agreement and entered into a new credit agreement ( the "credit facility" ) with third-party lenders .the credit facility includes a revolving credit facility of $ 1250 million , which may be drawn upon during a period of five years from november 22 , 2017 .the revolving credit facility includes a letter of credit subfacility of $ 500 million .the revolving credit facility has a variable interest rate on outstanding borrowings based on the london interbank offered rate ( "libor" ) plus a spread based upon the company's credit rating , which may vary between 1.125% ( 1.125 % ) and 1.500% ( 1.500 % ) .the revolving credit facility also has a commitment fee rate on the unutilized balance based on the company 2019s leverage ratio .the commitment fee rate as of december 31 , 2017 was 0.25% ( 0.25 % ) and may vary between 0.20% ( 0.20 % ) and 0.30% ( 0.30 % ) .the credit facility contains customary affirmative and negative covenants , as well as a financial covenant based on a maximum total leverage ratio .each of the company's existing and future material wholly owned domestic subsidiaries , except those that are specifically designated as unrestricted subsidiaries , are and will be guarantors under the credit facility .in july 2015 , the company used cash on hand to repay all amounts outstanding under a prior credit facility , including $ 345 million in principal amount of outstanding term loans .as of december 31 , 2017 , $ 15 million in letters of credit were issued but undrawn , and the remaining $ 1235 million of the revolving credit facility was unutilized .the company had unamortized debt issuance costs associated with its credit facilities of $ 11 million and $ 8 million as of december 31 , 2017 and 2016 , respectively .senior notes - in december 2017 , the company issued $ 600 million aggregate principal amount of unregistered 3.483% ( 3.483 % ) senior notes with registration rights due december 2027 , the net proceeds of which were used to repurchase the company's 5.000% ( 5.000 % ) senior notes due in 2021 in connection with the 2017 redemption described below .in november 2015 , the company issued $ 600 million aggregate principal amount of unregistered 5.000% ( 5.000 % ) senior notes due november 2025 , the net proceeds of which were used to repurchase the company's 7.125% ( 7.125 % ) senior notes due in 2021 in connection with the 2015 tender offer and redemption described below .interest on the company's senior notes is payable semi-annually .the terms of the 5.000% ( 5.000 % ) and 3.483% ( 3.483 % ) senior notes limit the company 2019s ability and the ability of certain of its subsidiaries to create liens , enter into sale and leaseback transactions , sell assets , and effect consolidations or mergers .the company had unamortized debt issuance costs associated with the senior notes of $ 15 million and $ 19 million as of december 31 , 2017 and 2016 , respectively. .

Question: what is the percentage change in the unamortized debt issuance costs associated with the senior notes from 2016 to 2017?
Answer: -21.1%