Methodology
The K15 Market Benchmark™, explained.
One number per model, powered by proprietary market intelligence and built from verified worldwide auction sales. No opinions, no unverified estimates — just the market record, measured.
Definition
The K15 Market Benchmark™ is Karbon Fifteen's proprietary measure of a model's current market value — powered by proprietary market intelligence and built from verified auction sales worldwide, in every major currency, normalized to USD including buyer's premium.
"Verified" means every input sale was confirmed against the primary auction-house record. Sales in GBP, EUR, CHF, JPY, and other currencies are converted at the exchange rate at the time of sale, so every model is comparable on one scale. The computation itself — how sales are screened, weighted, and combined — is proprietary to Karbon Fifteen. When a model has too few verified sales to support a reliable figure, no benchmark is shown.
From hammer to benchmark.
Collect
We continuously ingest public auction results from the world's leading auction houses and sale platforms, across every major collector-car market.
Verify
Each sale is checked against the primary auction-house record. Unverifiable results, withdrawn lots, and no-sales never enter the dataset.
Compute
Our proprietary K15 algorithm weighs each verified sale — screening outliers, adjusting for recency and sale context — to produce one benchmark per model.
Track
Trends and forecasts are computed only from that verified base — powered by proprietary market intelligence, so the number you see reflects the market as it stands.
Proprietary computation
Open about the inputs. Protective of the recipe.
We publish exactly what goes into the K15 Market Benchmark™: verified public auction sales, worldwide and in every major currency, normalized to USD including buyer's premium. Every input is traceable to a primary auction-house record you can check yourself.
How those sales become one number is Karbon Fifteen's intellectual property. The K15 algorithm screens statistical outliers, weights results by recency, and adjusts for sale context — restorations, competition variants, provenance-driven premiums — before producing the benchmark. The specific weightings and screening thresholds are proprietary and continuously refined against realized market results.
What we will always disclose: the benchmark uses only verified sales, it is powered by proprietary market intelligence, and it is withheld entirely when the data is too thin to support it.
The rules we never break.
Verified sales only
Every price behind the benchmark traces to a published, primary auction-house result — hammer plus premium in the sale's original currency, normalized to USD.
Outlier-resistant by design
A single headline record can distort a market read. The K15 computation is built to reflect what the middle of the market actually pays.
Recency-weighted
The computation favors the latest verified results, so the benchmark moves with the market rather than anchoring to history.
No number without data
If a model lacks sufficient verified sales, we show 'Insufficient history' — never a filler figure or an unverified estimate.
The numbers around the benchmark.
12-Month Trend
Annualized price movement derived from recent verified sales. Requires enough sales history to be reliable; otherwise we show 'Insufficient history'.
Forecast
A 12-month projection from proprietary trend models trained on decades of transactions. Always labeled as a projection — never a promise.
Record
The highest verified public sale for the model, with the auction house and date it was set.
Private / off-market estimate
Shown only where verified data supports it; quiet sales historically clear below auction headlines.
See the benchmark in action.
Every covered model — Powered by Proprietary Market Intelligence.