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: .

December 31
($ in millions)
2017
2016
Senior notes due December 15, 2021, 5.000%
—
600
Senior notes due November 15, 2025, 5.000%
600
600
Senior notes due December 1, 2027, 3.483%
600
—
Mississippi economic development revenue bonds due May 1, 2024, 7.81%
84
84
Gulf opportunity zone industrial development revenue bonds due December 1, 2028, 4.55%
21
21
Less unamortized debt issuance costs
(26)
(27)
Total long-term debt
1,279
1,278

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: Analyse this data from a financial earnings document. what is the percentage change in the unamortized debt issuance costs associated with the senior notes from 2016 to 2017?
Choices:
0.21053
0.52632
-0.21053
-0.2
-0.26667
Correct choice index: 2