Methodology
How 996Value.com values a 996
Every number on this site follows the rules on this page. If a figure ever conflicts with them, the rules win and the figure gets fixed.
The dataset
533 verified auction sales of 1999–2005 Porsche 911 (996) cars, each recorded by hand from the auction listing — never scraped, never estimated. Sources: Bring a Trailer, Cars & Bids, PCarMarket, Collecting Cars, and Hemmings. The dataset grows with weekly sweeps of new results.
Hammer-price basis
All sold figures are hammer prices: the winning bid, excluding buyer fees, so numbers reflect what the car sold for rather than the all-in transaction. Where a venue displays prices that already include a premium and the premium percentage cannot be verified from a primary source, those sales are held out of the dataset rather than guessed — the rule is: a price we cannot state exactly does not ship. Non-US prices are converted at the Bank of England daily spot rate for the sale date, with the rate recorded on the sale.
Valuation bands
- Valuations use sales from 2021 onward only; older sales appear in trend charts, not in bands.
- Bands are variant × mileage band. The headline figure is the band median, shown with the observed range and the count and date range of the sales behind it.
- Modified cars (engine swaps, forced-induction builds, safari conversions, per the listing notes) are excluded from bands. A stock engine replacement is not a modification and does not exclude a car.
- Bands combine transmissions. In the data, 6-speed manuals price toward the top of the observed range; no separate transmission adjustment is applied yet.
- A band holding only one or two sales prints those actual hammer prices instead of a valuation.
Measured adjustments (modifiers)
Adjustments are estimated by regression on the verified dataset and refreshed as the dataset grows. Only adjustments the data supports are applied in the calculator; the rest are tracked in the open.
| Adjustment | Effect | Status | Basis |
|---|---|---|---|
| IMS bearing replaced (documented) | +7.8% | Applied | Regression coefficient, verified sales dataset (367 cars), Oct 2026 |
| Recent bore scope (clean, documented) | — | Tracked, not applied | Not measurable in listing data at usable scale yet |
| Rear main seal replaced (documented) | — | Tracked, not applied | Usually bundled with IMS work; cannot be isolated yet |
| X51 Powerkit (factory) | — | Tracked, not applied | Too few X51 cars in the dataset |
| Factory Aerokit | — | Tracked, not applied | Fitment not yet recorded consistently |
| Factory hardtop (cabriolets) | None measured | Shown as a note | No measurable premium in this dataset |
Two effects the regression also measured, disclosed rather than adjusted: comparable cars bring about 18% less on Cars & Bids than on Bring a Trailer (a venue effect, not a market drop), and values trend about 5% per year across the period.
Asking prices
Asking prices live in a separate dataset (snapshots of PCA Mart and Rennlist listings, captured weekly) and are never blended into sold-price medians — asks run systematically above hammer prices. The ask-to-hammer spread is measured only on cars matched by VIN between the two datasets: same car, its asking record, then its auction result. Until enough matched pairs accumulate, the site shows the two figures side by side, labeled, and blends nothing.
Changelog
- October 19, 2026 — Multi-source dataset unified on one banded basis (2021+, stock, mileage-documented) across the calculator, model pages, and articles; modifier adjustments added to the calculator (IMS first).
- October 18, 2026 — Cars & Bids harvest completed and merged; dataset passed 500 verified sales.
- October 2026 — Asking-price dataset started (PCA Mart and Rennlist snapshots, VIN-keyed).