14 . accounting for certain long-lived assets eog reviews its proved oil and gas properties for impairment purposes by comparing the expected undiscounted future cash flows at a depreciation , depletion and amortization group level to the unamortized capitalized cost of the asset . the carrying rr values for assets determined to be impaired were adjusted to estimated fair value using the income approach described in the fair value measurement topic of the asc . in certain instances , eog utilizes accepted offers from third-party purchasers as the basis for determining fair value . during 2017 , proved oil and gas properties with a carrying amount of $ 370 million were written down to their fair value of $ 146 million , resulting in pretax impairment charges of $ 224 million . during 2016 , proved oil and gas properties with a carrying rr amount of $ 643 million were written down to their fair value of $ 527 million , resulting in pretax impairment charges of $ 116 million . impairments in 2017 , 2016 and 2015 included domestic legacy natural gas assets . amortization and impairments of unproved oil and gas property costs , including amortization of capitalized interest , were $ 211 million , $ 291 million and $ 288 million during 2017 , 2016 and 2015 , respectively . 15 . asset retirement obligations the following table presents the reconciliation of the beginning and ending aggregate carrying amounts of short-term and long-term legal obligations associated with the retirement of property , plant and equipment for the years ended december 31 , 2017 and 2016 ( in thousands ) : .
( 1 ) includes $ 164 million in 2016 related to yates transaction ( see note 17 ) . ( 2 ) includes settlements related to asset sales . the current and noncurrent portions of eog's asset retirement obligations are included in current liabilities - other and other liabilities , respectively , on the consolidated balance sheets. .
2017 2016
Carrying Amount at Beginning of Period $912,926 $811,554
Liabilities Incurred<sup>(1)</sup> 54,764 212,739
Liabilities Settled<sup>(2)</sup> (61,871) (94,800)
Accretion 34,708 32,306
Revisions (9,818) (38,286)
Foreign Currency Translations 16,139 (10,587)
Carrying Amount at End of Period $946,848 $912,926
Current Portion $19,259 $18,516
Noncurrent Portion $927,589 $894,410
2017 2016
carrying amount at beginning of period $ 912926 $ 811554
liabilities incurred ( 1 ) 54764 212739
liabilities settled ( 2 ) -61871 ( 61871 ) -94800 ( 94800 )
accretion 34708 32306
revisions -9818 ( 9818 ) -38286 ( 38286 )
foreign currency translations 16139 -10587 ( 10587 )
carrying amount at end of period $ 946848 $ 912926
current portion $ 19259 $ 18516
noncurrent portion $ 927589 $ 894410
considering the years 2016 and 2017 , what is the increase observed in accretion?