Transparency
Our XGBoost model is validated against a 20% holdout set every week. Here are the latest numbers — unfiltered, by market segment.
v2.1 improvement: R² up from 71.7% to 83.1% (+11.4pts) · MAPE down from 25.7% to 28.9% (--3.2pts) · 231 statistical outliers filtered via MAD
Gradient-boosted regression trained on log-transformed prices across 22 engineered features — generation, trim, year, mileage, car age, transmission, color tier, geography, premium options, platform dynamics, seasonality, and interaction terms.
Model retrains weekly on 2,940 samples with a 735-sample holdout set stratified by market segment. Recency-weighted (6-month half-life) with MAD-based outlier filtering and Bayesian prior blending for thin segments.
Mean Absolute Percentage Error measures average prediction distance. Lower is better. Under 15% = high confidence. Under 25% = good. Above 25% = fair.
Sample of holdout validation results (735 sales withheld from training). Model v2.1.
Carrera, Targa, Turbo, GTS, Speedster — 930 through 992
R²
81.5%
MAPE
23.9%
Holdout n
524
GT3, GT3 RS, GT2, GT2 RS, GT4, GT4 RS, R, S/T, Sport Classic
R²
38.4%
MAPE
138.6%
Holdout n
40
986, 987, 981, 718 — all trims including GT4 & Spyder
R²
92.5%
MAPE
18.9%
Holdout n
171
Real holdout predictions where the model nailed the sale price.
2018 911 GT3 (991.2)
Manual, 8k miles, Guards Red
Predicted
$178,500
Sold For
$181,000
Error
1.4%
2015 Cayman GTS (981c)
PDK, 32k miles, Sapphire Blue
Predicted
$54,200
Sold For
$52,750
Error
2.7%
2020 911 Carrera S (992)
PDK, 14k miles, GT Silver
Predicted
$109,800
Sold For
$112,000
Error
2.0%
What drives the price prediction most, ranked by XGBoost feature importance.
Last retrained June 29, 2026. Metrics refresh automatically with each weekly retrain.
Weekly market intelligence delivered free. See the data behind every Porsche price.