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 .

For the Years Ended December 31,
Variance
(in millions)
2017
2016
$
%
Cost of sales
$10,432
$9,391
$1,041
11.1%
Marketing, administration and research costs
6,725
6,405
320
5.0%
Operating income
11,503
10,815
688
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: Analyse this data from a financial earnings document. what is the percentage increase in interest expense?
Choices:
0.03143
25813.69248
0.02517
0.02581
0.02455
Correct choice index: 3