Two cars of the same age can hold very different proportions of their original price. Depreciation tracks the used market's assessment of future ownership cost and available supply.
The steepest fall happens immediately
A new vehicle loses a substantial share of its value on first registration, because it moves from a market with warranty, finance offers and choice of specification into one without them.
Manufacturer discounts widen the gap further. Where new cars are routinely sold below list price, the used market prices against the real transaction price rather than the published one.
This is why models sold heavily with incentives depreciate faster than models sold at or near list, even when the two are otherwise comparable in quality.
Supply of near-identical examples matters most
Vehicles bought in fleets and returned from lease contracts arrive on the used market in batches, in similar specification and condition, at the same time.
That concentration of supply depresses prices for that model specifically, regardless of how well the vehicle is regarded by the people driving it.
Models sold mainly to private buyers reach the used market gradually and in varied specification, which supports values simply because no single batch floods the listings.
Expected repair liability is priced in
A used buyer is purchasing the remaining life of every component, so a model with a reputation for expensive failures sells at a discount that reflects the risk.
Parts availability, the number of specialists able to work on the vehicle and the cost of routine service items all feed into that assessment.
Complex technology accelerates the effect. Systems that are expensive to replace and difficult to diagnose reduce the value of an otherwise sound car as it ages.
The curve flattens rather than continuing
After the early years, the annual percentage loss falls sharply, because the remaining value is increasingly supported by the vehicle's usefulness as transport.
At the bottom, values are set by mechanical condition rather than by brand or specification, and two very different cars can converge on similar figures.
A small number of models reverse the trend after long periods, but that depends on scarcity and enthusiast demand rather than on anything predictable at purchase.
Condition evidence is what protects value
Documented service history, matching records and evidence of consistent maintenance reduce the buyer's uncertainty, and uncertainty is what produces discounts.
Mileage functions as a proxy for wear, but its influence is smaller on vehicles where a documented history offers direct evidence of how the car was treated.
Colour, specification and transmission choice also affect resale in ways that differ by market, since the used buyer pool is not the same as the original one.