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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 82.8% (+11.1pts) · MAPE down from 25.7% to 36.8% (--11.1pts) · 295 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 3,226 samples with a 807-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 (807 sales withheld from training). Model v2.1.
Carrera, Targa, Turbo, GTS, Speedster — 930 through 992
R²
79.3%
MAPE
34.6%
Holdout n
595
GT3, GT3 RS, GT2, GT2 RS, GT4, GT4 RS, R, S/T, Sport Classic
R²
56.1%
MAPE
130.7%
Holdout n
43
986, 987, 981, 718 — all trims including GT4 & Spyder
R²
93.8%
MAPE
20.5%
Holdout n
169
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 October 5, 2026. Metrics refresh automatically with each weekly retrain.
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