Estimated useful lives by each type of asset category are as follows:
Years
Buildings
Up to 39
Leasehold improvementsLesser of (i) expected useful life of improvement or (ii) life of lease (including likely extension thereof)
Machinery and equipment
1 to 10
Property, plant and equipment by type were as follows:
(in thousands)As of December 31,
Property, Plant and Equipment20242023
Leasehold improvements$8,352 $6,987 
Machinery and equipment48,643 46,964 
Construction in progress2,454 1,654 
Total property, plant and equipment, at cost59,449 55,605 
Accumulated depreciation(44,043)(40,677)
Property, plant and equipment, net$15,406 $14,928 

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.