american tower corporation and subsidiaries notes to consolidated financial statements assessments of expected future cash flows over the period in which the obligation is expected to be settled and applies a discount factor that captures the uncertainties associated with the obligation .
changes in these unobservable inputs could significantly impact the fair value of the liabilities recorded in the accompanying consolidated balance sheets and adjustments recorded in the consolidated statements of operations .
as of december 31 , 2014 , the company estimates that the value of all potential acquisition-related contingent consideration required payments to be between zero and $ 40.4 million .
during the years ended december 31 , 2014 and 2013 , the fair value of the contingent consideration changed as follows ( in thousands ) : .

2014
2013
Balance as of January 1
$31,890
$23,711
Additions
6,412
13,474
Settlements
(3,889)
(8,789)
Change in fair value
(225)
5,743
Foreign currency translation adjustment
(4,934)
(2,249)
Other (1)
(730)
—
Balance as of December 31
$28,524
$31,890

( 1 ) in connection with the sale of operations in panama , the buyer assumed the company 2019s potential obligations related to additional purchase price consideration .
items measured at fair value on a nonrecurring basis assets held and used 2014the company 2019s long-lived assets are measured at fair value on a nonrecurring basis using level 3 inputs .
during the year ended december 31 , 2014 , certain long-lived assets held and used with a carrying value of $ 8900.0 million were written down to their net realizable value of $ 8888.8 million as a result of an asset impairment charge of $ 11.2 million .
during the year ended december 31 , 2013 , certain long-lived assets held and used with a carrying value of $ 8554.5 million were written down to their net realizable value of $ 8538.6 million , as a result of an asset impairment charge of $ 15.9 million .
the asset impairment charges are recorded in other operating expenses in the accompanying consolidated statements of operations .
these adjustments were determined by comparing the estimated proceeds from the sale of assets or the estimated fair value utilizing projected future discounted cash flows to be provided from the long-lived assets to the asset 2019s carrying value .
during the year ended december 31 , 2014 , nii , a u.s .
corporation , filed for chapter 11 bankruptcy protection on behalf of itself and certain of its subsidiaries .
nii is the ultimate parent company of certain operating subsidiaries in brazil , chile and mexico that collectively represent approximately 6% ( 6 % ) of the company 2019s consolidated revenues for the year ended december 31 , 2014 .
none of these subsidiaries were included in nii 2019s chapter 11 filing .
the company 2019s assessment of the impact of the proceedings did not identify any indicators of impairment as of december 31 , 2014 .
sale of assets 2014during the year ended december 31 , 2014 , the company completed the sale of its operations in panama and its third-party structural analysis business for an aggregate sale price of $ 17.9 million , plus a working capital adjustment .
at the time of sale , the carrying amount of these assets primarily included $ 8.1 million of property and equipment , $ 7.8 million of intangible assets and $ 3.6 million of goodwill .
the company recorded a net charge of $ 2.2 million in other operating expenses in the accompanying consolidated statements of operations .
there were no other items measured at fair value on a nonrecurring basis during the year ended december 31 .

Question: Analyse this data from a financial earnings document. was the change in asset impairment charges between 2014 and 2013 in us$ m?
Choices:
-4.7
-12.9
-2.5
6396.1
-6.7
Correct choice index: 0