Property, plant, and equipment were composed of the following:


	December 31
Millions of dollars	2020		2019
Land	$	120	$	202
Buildings and property improvements	1,652		3,167
Machinery, equipment, and other	13,592		16,571
Total	15,364		19,940
Less accumulated depreciation	11,039		12,630
Net property, plant, and equipment	$	4,325	$	7,310

During the year ended December 31, 2020, a $2.3 billion impairment charge was recorded related to property, plant, and equipment. See Note 2 to the consolidated financial statements for further discussion on impairments and other charges.

Classes of assets are depreciated over the following useful lives:


	Buildings and Property Improvements
	2020	2019
1 - 10 years	13%	12%
11 - 20 years	41%	41%
21 - 30 years	21%	22%
31 - 40 years	25%	25%


	Machinery, Equipment, and Other
	2020	2019
1 - 5 years	49%	43%
6 - 10 years	41%	47%
11 - 20 years	10%	10%