{"pre_text": ["united parcel service , inc .", "and subsidiaries notes to consolidated financial statements 8.375% ( 8.375 % ) debentures the 8.375% ( 8.375 % ) debentures consist of two separate tranches , as follows : 2022 $ 276 million of the debentures have a maturity of april 1 , 2030 .", "these debentures have an 8.375% ( 8.375 % ) interest rate until april 1 , 2020 , and , thereafter , the interest rate will be 7.62% ( 7.62 % ) for the final 10 years .", "these debentures are redeemable in whole or in part at our option at any time .", "the redemption price is equal to the greater of 100% ( 100 % ) of the principal amount and accrued interest , or the sum of the present values of the remaining scheduled payout of principal and interest thereon discounted to the date of redemption ( at a benchmark treasury yield plus five basis points ) plus accrued interest .", "2022 $ 424 million of the debentures have a maturity of april 1 , 2020 .", "these debentures are not subject to redemption prior to maturity .", "interest is payable semiannually in april and october for both tranches and neither tranche is subject to sinking fund requirements .", "we subsequently entered into interest rate swaps on the 2020 debentures , which effectively converted the fixed interest rates on the debentures to variable libor-based interest rates .", "the average interest rate payable on the 2020 debentures , including the impact of the interest rate swaps , for 2016 and 2015 was 5.43% ( 5.43 % ) and 5.04% ( 5.04 % ) , respectively .", "floating rate senior notes the floating rate senior notes bear interest at either one or three-month libor , less a spread ranging from 30 to 45 basis points .", "the average interest rate for 2016 and 2015 was 0.21% ( 0.21 % ) and 0.01% ( 0.01 % ) , respectively .", "these notes are callable at various times after 30 years at a stated percentage of par value , and putable by the note holders at various times after 10 years at a stated percentage of par value .", "the notes have maturities ranging from 2049 through 2066 .", "in march , june and august 2016 , we issued floating rate senior notes in principal balances of $ 118 , $ 74 and $ 35 million , respectively .", "these notes bear interest at three-month libor less 30 basis points and mature in 2066 .", "capital lease obligations we have certain property , plant and equipment subject to capital leases .", "some of the obligations associated with these capital leases have been legally defeased .", "the recorded value of our property , plant and equipment subject to capital leases is as follows as of december 31 ( in millions ) : ."], "post_text": ["these capital lease obligations have principal payments due at various dates from 2017 through 3005. ."], "table": [["", "2016", "2015"], ["vehicles", "$ 68", "$ 74"], ["aircraft", "2291", "2289"], ["buildings", "190", "207"], ["accumulated amortization", "-896 ( 896 )", "-849 ( 849 )"], ["property plant and equipment subject to capital leases", "$ 1653", "$ 1721"]], "table_ori": [["", "2016", "2015"], ["Vehicles", "$68", "$74"], ["Aircraft", "2,291", "2,289"], ["Buildings", "190", "207"], ["Accumulated amortization", "(896)", "(849)"], ["Property, plant and equipment subject to capital leases", "$1,653", "$1,721"]]}

Question: what was the change in millions of vehicles from 2015 to 2016?
Evidence:
table_1: the vehicles of 2016 is $ 68 ; the vehicles of 2015 is $ 74 ;
Program: subtract(68, 74)
Answer:
str_answer: -6
exe_answer: -6