NOTE 4—PROPERTY

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A summary of property is as follows:

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Property is recorded at cost or fair value, in the case of property resulting from acquisitions. The Company uses the straight-line method in computing depreciation and amortization for financial reporting purposes. The estimated useful lives for leasehold improvements and buildings subject to a ground lease reflect the shorter of the expected useful lives of the assets or the base terms of the corresponding lease agreements plus renewal options expected to be exercised for these leases for assets placed in service subsequent to the lease inception. The estimated useful lives are as follows:

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Expenditures for additions (including interest during construction) and betterments are capitalized, and expenditures for maintenance and repairs are charged to expense as incurred. The cost of assets retired or otherwise disposed of and the related accumulated depreciation and amortization are eliminated from the accounts in the year of disposal. Gains or losses resulting from property disposals are included in operating expense in the accompanying consolidated statements of operations.

Depreciation expense was $453.2 million, $413.6 million, and $498.2 million for the years ended December 31, 2020, December 31, 2019 and December 31, 2018, respectively.