Property, plant and equipment - net consisted of the following:
December 31,
(Millions)20252024
Property, plant and equipment - at cost
Buildings and leasehold improvements
$870 $956 
Machinery and equipment
1,824 2,150 
Construction in progress499 504 
Gross property, plant and equipment3,193 3,610 
Accumulated depreciation(1,867)(1,988)
Property, plant and equipment - net$1,326 $1,622 
Depreciation expense consisted of the following:
Year ended December 31,
(Millions)202520242023
Depreciation expense$151 $181 $164 

About PP&E Disclosures

The PP&E disclosure details a company's physical asset base — land, buildings, machinery, and equipment — along with the depreciation methods and useful life assumptions that determine how these costs flow through the income statement. Capitalization policy thresholds reveal management's judgment on the boundary between expense and asset, directly affecting both reported earnings and asset values.

Key signals: changes in estimated useful lives or depreciation methods can materially shift reported earnings without any operational change. Compare capital expenditures against depreciation expense — when capex consistently trails depreciation, the asset base may be aging and underinvested. Watch for large asset impairments or write-downs that signal overvalued carrying amounts. Asset retirement obligations reveal future environmental or decommissioning costs that are often underappreciated. Compare PP&E intensity (PP&E-to-revenue) against industry peers to assess capital efficiency and competitive positioning.