In 2015 and 2014, U.S. Cellular and TDS Telecom performed a review of the assumptions and estimated costs related to asset retirement obligations. The results of the reviews (identified as “Revisions in estimated cash outflows”) and other changes in asset retirement obligations during 2015 and 2014 were as follows:

		2015		2014
(Dollars in thousands)
Balance at beginning of year		$	239,032	$	275,238
	Additional liabilities accrued		1,661		4,907
	Revisions in estimated cash outflows		(3,669)		(992)
	Disposition of assets		(9,684)		(46,242)
	Accretion expense		15,735		17,506
	Transferred to Liabilities held for sale		–		(11,385)
Balance at end of year¹		$	243,075	$	239,032

1	The total amount of asset retirement obligations related to the Divestiture Transaction and Airadigm Transaction included in Other current liabilities was $9.1 million as of December 31, 2014.