Property, plant, and equipment are recorded at cost, net of accumulated depreciation and impairments. Costs of routine maintenance and repair are expensed when incurred.

The Company capitalizes certain qualified costs incurred in connection with the development of software used internally. Costs incurred during the application development stage are evaluated to determine whether the costs meet the criteria for capitalization. Costs related to preliminary project activities and post implementation activities, including maintenance, are expensed as incurred.

Property, plant, and equipment are primarily depreciated using the straight-line method over the estimated useful life of the asset. Leasehold improvements are amortized over the period of lease or the life of the asset, whichever is shorter, using the straight-line method. Capitalized costs related to software used internally are amortized using the straight-line method over the estimated useful life of the asset. Land is not depreciated.

The following table summarizes the components of “Property, plant, and equipment, net” (in millions):


	Estimated Useful Lives	December 31, 2020		December 31, 2021
Land, buildings, and building improvements	10 to 30 years	$	88	$	429
Leasehold improvements	Shorter of 10 years or lease term	51		191
Machinery, equipment, vehicles, and office furniture	5 to 15 years	88		1,856
Computer equipment, hardware, and software	3 to 10 years	51		180
Construction in progress		1,205		760
Total property, plant, and equipment		1,483		3,416
Accumulated depreciation and amortization		(38)		(233)
Total property, plant, and equipment, net		$	1,445	$	3,183

Depreciation and amortization expense was $7 million, $29 million, and $197 million for the years ended December 31, 2019, 2020 and 2021, respectively.