net revenues include $ 3.8 billion in 2017 and $ 739 million in 2016 related to the sale of rrps , mainly driven by japan . these net revenue amounts include excise taxes billed to customers . excluding excise taxes , net revenues for rrps were $ 3.6 billion in 2017 and $ 733 million in 2016 . in some jurisdictions , including japan , we are not responsible for collecting excise taxes . in 2017 , approximately $ 0.9 billion of our $ 3.6 billion in rrp net revenues , excluding excise taxes , were from iqos devices and accessories . excise taxes on products increased by $ 1.1 billion , due to : 2022 higher excise taxes resulting from changes in retail prices and tax rates ( $ 4.6 billion ) , partially offset by 2022 favorable currency ( $ 1.9 billion ) and 2022 lower excise taxes resulting from volume/mix ( $ 1.6 billion ) . our cost of sales ; marketing , administration and research costs ; and operating income were as follows : for the years ended december 31 , variance .

Table: ( in millions ) for the years ended december 31 , 2017 for the years ended december 31 , 2016 for the years ended december 31 , $ % (  % ) cost of sales $ 10432 $ 9391 $ 1041 11.1% ( 11.1 % ) marketing administration and research costs 6725 6405 320 5.0% ( 5.0 % ) operating income 11503 10815 688 6.4% ( 6.4 % )

cost of sales increased by $ 1.0 billion , due to : 2022 higher cost of sales resulting from volume/mix ( $ 1.1 billion ) , partly offset by 2022 lower manufacturing costs ( $ 36 million ) and 2022 favorable currency ( $ 30 million ) . marketing , administration and research costs increased by $ 320 million , due to : 2022 higher expenses ( $ 570 million , largely reflecting increased investment behind reduced-risk products , predominately in the european union and asia ) , partly offset by 2022 favorable currency ( $ 250 million ) . operating income increased by $ 688 million , due primarily to : 2022 price increases ( $ 1.4 billion ) , partly offset by 2022 higher marketing , administration and research costs ( $ 570 million ) and 2022 unfavorable currency ( $ 157 million ) . interest expense , net , of $ 914 million increased by $ 23 million , due primarily to unfavorably currency and higher average debt levels , partly offset by higher interest income . our effective tax rate increased by 12.8 percentage points to 40.7% ( 40.7 % ) . the 2017 effective tax rate was unfavorably impacted by $ 1.6 billion due to the tax cuts and jobs act . for further details , see item 8 , note 11 . income taxes to our consolidated financial statements . we are continuing to evaluate the impact that the tax cuts and jobs act will have on our tax liability . based upon our current interpretation of the tax cuts and jobs act , we estimate that our 2018 effective tax rate will be approximately 28% ( 28 % ) , subject to future regulatory developments and earnings mix by taxing jurisdiction . we are regularly examined by tax authorities around the world , and we are currently under examination in a number of jurisdictions . it is reasonably possible that within the next 12 months certain tax examinations will close , which could result in a change in unrecognized tax benefits along with related interest and penalties . an estimate of any possible change cannot be made at this time . net earnings attributable to pmi of $ 6.0 billion decreased by $ 932 million ( 13.4% ( 13.4 % ) ) . this decrease was due primarily to a higher effective tax rate as discussed above , partly offset by higher operating income . diluted and basic eps of $ 3.88 decreased by 13.4% ( 13.4 % ) . excluding .

Question: what is the percentage increase in interest expense?
Answer: 2.6%
Calculation: divide(23, subtract(914, 23))