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, 2019	$	5,016		$	840	$	767		$	1,945		$	8,568
Accumulated impairment charges		—			—		(133	)		(1,551	)		(1,684	)
Balance as of May 31, 2019		5,016			840		634			394			6,884
Impairment charges		—			—		—			(358	)		(358	)
Other⁽¹⁾		(147	)		—		—			(7	)		(154	)
Balance as of May 31, 2020		4,869			840		634			29			6,372
Goodwill acquired⁽²⁾		18			103		—			40			161
Other⁽¹⁾		471			—		—			(12	)		459
Balance as of May 31, 2021	$	5,358		$	943	$	634		$	57		$	6,992
Accumulated goodwill impairment charges as of May 31, 2021	$	—		$	—	$	(133	)	$	(1,909	)	$	(2,042	)

Our reporting units with significant recorded goodwill include FedEx Express, FedEx Ground and FedEx Freight. We evaluated these reporting units during the fourth quarter and the estimated fair value of each of these reporting units exceeded their carrying values as of the end of 2021 and 2020; therefore, we do not believe that any of these reporting units were impaired as of the balance sheet dates.

In 2020, we recorded impairment charges of $358 million predominantly attributable to our FedEx Office and Print Services, Inc. (“FedEx Office”) reporting unit. The coronavirus (“COVID-19”) pandemic resulted in store closures and declining print revenue at FedEx Office during the fourth quarter of 2020. 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. No impairments of goodwill were recognized during 2021 or 2019.

OTHER INTANGIBLE ASSETS. The summary of our intangible assets and related accumulated amortization at May 31, 2021 and 2020 is as follows (in millions):

	2021							2020
	Gross Carrying Amount		Accumulated Amortization			Net Book Value		Gross Carrying Amount		Accumulated Amortization			Net Book Value
Customer relationships	$	591	$	(299	)	$	292	$	641	$	(327	)	$	314
Technology		65		(35	)		30		65		(57	)		8
Trademarks and other		1		(1	)		—		132		(132	)		—
Total	$	657	$	(335	)	$	322	$	838	$	(516	)	$	322

Amortization expense for intangible assets was $49 million in 2021, $66 million in 2020 and $82 million in 2019.

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