Property, Plant and Equipment Property and equipment are initially recorded at cost. Gains or losses on disposition are recognized as earned or incurred. Costs of major improvements are capitalized, while costs of normal repairs and maintenance are charged to expense as incurred. The following table summarizes the Company's property and equipment balances and includes the estimated useful lives that are generally used to depreciate the assets on a straight-line basis: As of January 31, (Amounts in millions) Estimated Useful Lives 2018 2017 Land N/A 25,298 24,801 Buildings and improvements 3-40 years 101,155 98,547 Fixtures and equipment 1-30 years 52,695 48,998 Transportation equipment 3-15 years 2,387 2,845 Construction in progress N/A 3,619 4,301 Property and equipment 185,154 S 179,492 Accumulated depreciation (77,479 (71,782 Property and equipment, net 107,675 107,710 $ $ s Leasehold improvements are depreciated or amortized over the shorter of the estimated useful life of the asset or the remaining expected lease term. Total depreciation and amortization expense for property and equipment, property under financing obligations and property under capital leases for fiscal 2018 and 2017 was $10,532 million, $9,580 million, respectively. You note that Walmart's Average Useful Life calculation has increased dramatically from similar calculations in prior years. Why is this a concern for an analyst? (5 points)