During the year ended December 31, 2021, we purchased certain intangible assets and completed several business acquisitions that were not material to our consolidated financial statements, individually and in aggregate. Accordingly, pro forma historical results of operations related to these business acquisitions during the year ended December 31, 2021 have not been presented. We have included the financial results of these business acquisitions in our consolidated financial statements from their respective dates of acquisition.

Goodwill generated from all business acquisitions completed was primarily attributable to expected synergies from future growth and potential monetization opportunities. The amount of goodwill generated that was deductible for tax purposes was not material.

Changes in the carrying amount of goodwill by reportable segment for the years ended December 31, 2021 and 2020 are as follows (in millions):


	Family of Apps		Reality Labs		Total
Balance as of December 31, 2019					$	18,715
Acquisitions					322
Effect of currency translation adjustment					13
Balance as of December 31, 2020					19,050
Acquisitions					210
Adjustments/transfer					(191)
Effect of currency translation adjustment					(4)
Segment allocation in the fourth quarter of 2021 (1)	$	18,455	$	610	19,065
Acquisitions in the fourth quarter of 2021	—		128		128
Effect of currency translation adjustment	3		1		4
Balance as of December 31, 2021	$	18,458	$	739	$	19,197

(1)Represents reallocation of goodwill as a result of our change in segments in the fourth quarter of 2021. See Note 15 — Segment and Geographical Information for further details.

The following table sets forth the major categories of the intangible assets and the weighted-average remaining useful lives for those assets that are not already fully amortized (in millions):


		December 31, 2021						December 31, 2020
	Weighted-Average Remaining Useful Lives (in years)	Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization		Net Carrying Amount
Acquired users	0.0	$	2,057	$	(2,057)	$	—	$	2,057	$	(1,840)	$	217
Acquired technology	2.6	1,412		(1,169)		243		1,297		(1,088)		209
Acquired patents	3.4	827		(722)		105		805		(677)		128
Trade names	3.0	644		(633)		11		636		(622)		14
Other	12.1	176		(167)		9		223		(168)		55
Total finite-lived assets		5,116		(4,748)		368		5,018		(4,395)		623
Total indefinite-lived assets	N/A	266		—		266		—		—		—
Total intangible assets, net		$	5,382	$	(4,748)	$	634	$	5,018	$	(4,395)	$	623

Amortization expense of intangible assets for the years ended December 31, 2021, 2020, and 2019 was $407 million, $473 million, and $562 million, respectively.

As of December 31, 2021, expected amortization expense for the unamortized finite-lived intangible assets for the next five years and thereafter is as follows (in millions):