GOODWILL. The carrying amount of goodwill attributable to each reportable operating segment and changes therein are as follows (in millions):

	FedEx Express Segment			FedEx Ground Segment		FedEx Freight Segment			Corporate, Other and Eliminations			Total
Goodwill at May 31, 2018	$	5,100		$	840	$	767		$	1,950		$	8,657
Accumulated impairment charges		—			—		(133	)		(1,551	)		(1,684	)
Balance as of May 31, 2018		5,100			840		634			399			6,973
Goodwill acquired⁽¹⁾		126			—		—			—			126
Other⁽²⁾		(210	)		—		—			(5	)		(215	)
Balance as of May 31, 2019		5,016			840		634			394			6,884
Impairment charges		—			—		—			(358	)		(358	)
Other⁽²⁾		(147	)		—		—			(7	)		(154	)
Balance as of May 31, 2020	$	4,869		$	840	$	634		$	29		$	6,372
Accumulated goodwill impairment charges as of May 31, 2020	$	—		$	—	$	(133	)	$	(1,909	)	$	(2,042	)

We recorded an impairment charge of $358 million attributable to our FedEx Office and Print Services, Inc. (“FedEx Office”) and FedEx Supply Chain Distribution System, Inc. (“FedEx Supply Chain”) reporting units in the fourth quarter of 2020. The COVID-19 pandemic resulted in store closures and declining print revenue at FedEx Office during the fourth quarter of 2020 and is expected to continue to negatively impact its near-term operating performance. Based on these factors, our outlook for the FedEx Office business and retail industry changed in the fourth quarter of 2020, which contributed $348 million to the goodwill impairment charge.

While there are several factors negatively impacting near-term results at FedEx Express, including weak global economic conditions and the timing and amount of TNT Express integration program expenses, FedEx Express continues to be an established profitable business with a fair value that exceeds its carrying value based on our valuation performed during the fourth quarter of 2020. In addition, our other reporting units with significant recorded goodwill include FedEx Ground and FedEx Freight. We evaluated these reporting units during the fourth quarters of 2020 and 2019. The estimated fair value of each of these reporting units significantly exceeded their carrying values as of the end of 2020 and 2019; therefore, we do not believe that any of these reporting units were impaired as of the balance sheet dates. No impairments of goodwill were recognized in 2019.

In 2018, we incurred a goodwill impairment charge of $374 million related to FedEx Supply Chain, eliminating substantially all of the goodwill attributable to this reporting unit. In our evaluation of the goodwill of this reporting unit, we compared the fair value of the reporting unit to its carrying value (including attributable goodwill). Fair value was estimated using standard valuation methodologies (principally the income and market approach classified as Level 3 within the fair value hierarchy) incorporating market participant considerations and management’s assumptions on revenue growth rates, operating margins, discount rates and expected capital expenditures. The key factors contributing to the goodwill impairment were underperformance of the FedEx Supply Chain business during 2018, including base business erosion, and the failure to attain the level of operating synergies and revenue and profit growth anticipated at the time of the acquisition. Based on these factors, our outlook for the business and industry changed in the fourth quarter of 2018.

OTHER INTANGIBLE ASSETS. The summary of our intangible assets and related accumulated amortization at May 31, 2020 and 2019 is as follows (in millions):

	2020							2019
	Gross Carrying Amount		Accumulated Amortization			Net Book Value		Gross Carrying Amount		Accumulated Amortization			Net Book Value
Customer relationships	$	641	$	(327	)	$	314	$	685	$	(293	)	$	392
Technology		65		(57	)		8		66		(51	)		15
Trademarks and other		132		(132	)		—		137		(128	)		9
Total	$	838	$	(516	)	$	322	$	888	$	(472	)	$	416

Amortization expense for intangible assets was $66 million in 2020, $82 million in 2019 and $87 million in 2018.

Expected amortization expense for the next five years is as follows (in millions):