Depreciation is the systematic allocation of a tangible asset's cost over its useful life, spreading the expense across the years the asset generates revenue rather than recording the entire cost at once.
Straight-Line: (Cost − Salvage Value) ÷ Useful Life
Double-Declining Balance: (2 ÷ Useful Life) × Book Value at Start of Year
A company buys manufacturing equipment for $1,000,000 with a 10-year useful life and $100,000 salvage value. Under straight-line depreciation: ($1,000,000 − $100,000) ÷ 10 = $90,000 per year. Each year, the income statement shows a $90,000 depreciation expense, and the balance sheet reduces the asset's book value by $90,000. After 5 years, the accumulated depreciation is $450,000, and the net book value is $550,000. Under double-declining balance, year 1 depreciation would be (2 ÷ 10) × $1,000,000 = $200,000 — much higher in early years.
Depreciation is a non-cash expense — it reduces reported earnings but doesn't actually consume cash. This distinction is crucial for understanding a company's true cash generation. A company reporting $1 million in net income with $500,000 in depreciation expense actually generated $1.5 million in operating cash flow. Depreciation merely spreads the cash outflow (which occurred when the asset was purchased) over the asset's useful life for accounting purposes.
The choice of depreciation method significantly affects reported earnings and tax liability. Accelerated methods (like double-declining balance) front-load expenses, reducing early-year profits but deferring taxes. Straight-line depreciation produces uniform expenses and smoother earnings. For tax purposes in the U.S., companies often use accelerated depreciation (MACRS) to minimize current tax payments, while using straight-line for financial reporting to show smoother earnings to investors.
Depreciation also plays a key role in capital-intensive industries like airlines, manufacturing, and telecommunications. An airline's depreciation expense on its fleet can be billions annually, creating a large gap between earnings and cash flow. Understanding this gap is essential for valuing such businesses — a low P/E ratio for an airline might be misleading because depreciation is understating cash generation, or conversely, the airline might be under-investing in fleet renewal.
Amazon (AMZN) uses depreciation extensively. Its massive network of fulfillment centers, data centers, and delivery vehicles generates billions in annual depreciation expense — approximately $40 billion in 2023. This depreciation reduces Amazon's reported earnings significantly, making its PE ratio appear extremely high. However, Amazon's actual cash flow is much higher because depreciation is a non-cash charge. This is why many Amazon investors focus on operating cash flow or free cash flow rather than net income.
Always check EBITDA and free cash flow alongside earnings: For capital-intensive businesses, net income can be misleading because depreciation distorts the picture. EBITDA and FCF give a clearer view of actual cash generation.
Compare depreciation to capital expenditures: If depreciation is $10M/year but capex is $15M/year, the company is expanding (good). If depreciation is $10M and capex is only $5M, the company may be under-investing and eating its future (bad).
Watch for depreciation policy changes: Management can boost earnings by extending useful lives or increasing salvage values, reducing annual depreciation expense. This is an accounting change, not a real improvement.
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Depreciation shows how much a company's physical assets are wearing out or becoming obsolete each year. High depreciation relative to revenue means the company has significant capital expenditure requirements. Low depreciation might indicate underinvestment. Compare depreciation to capex — if capex consistently exceeds depreciation, the company is growing its asset base.
Straight-line vs. accelerated depreciation?
Straight-line spreads cost evenly over the asset's life (e.g., $10K/year for 5 years). Accelerated (like double-declining balance) front-loads expenses — higher early, lower later. Companies often use accelerated depreciation for tax purposes (more deductions now) but straight-line for reporting (smoother earnings).
Is depreciation a real expense?
It's a non-cash expense — no actual cash leaves the company. This is why EBITDA (which adds back depreciation) is popular for comparing companies. However, depreciation represents real economic costs: equipment eventually needs replacement. Companies that ignore depreciation in their financial planning will face cash crunches when assets need replacing.