Vrai-Prix
Your property's true value, no black box
A transparent valuation engine for every property in Quebec — 3.7 million properties, 745,119 real sales, and every calculation shown in full.
3,747,008
properties covered
745,119
real sales
11.0%
median error (MdAPE)
0.995
median ratio (IAAO target 0.90–1.10)
99.88%
spatial match rate
$2.01T
total provincial value computed
Overview
Vrai-Prix estimates the market value of any Quebec property — single-family homes, plexes, condos, cottages, land — and shows exactly why: every comparable sale, every dollar adjustment, the model weighting, the value range, and a mandatory A–D confidence grade. The differentiator is total transparency: no magic score, no black box.
The engine fuses two approaches: a LightGBM hedonic model trained on log-prices with 18 variables and quantile heads for P10–P90 ranges (65% weight), blended with a weighted median of market-, size-, and age-adjusted comparable sales (35%). Six assessment-roll vintages — 22,150,285 observations from Quebec's open MAMH data — feed 22 million pre-computed estimates.
Validation follows the IAAO ratio-study standard on 102,943 never-seen sales: 11.0% median error, a 0.995 median ratio squarely inside the 0.90–1.10 target, and 72.1% of estimates within ±20% of the actual price. A strict temporal test on 68,364 sales from 2026 confirms out-of-time robustness.
Key Features
Full-text address search
SQLite FTS5 search across all 3,747,008 assessment units in the province, with instant autocompletion.
Hybrid estimation engine
65% LightGBM hedonic model plus 35% weighted-median adjusted comparables, with every adjustment displayed in dollars — market conditions, size, and age.
Ranges with mandatory confidence
P10–P90 ranges from quantile regression and an A–D confidence grade driven by comparable count, dispersion, and range width — never hidden.
Surveyor-style comparables map
A hand-built pure-SVG 'surveyor's plan' with real azimuths and distances — zero map tiles, zero third-party dependencies.
Data-drawn property portrait
An SVG facade drawn from registry data, a to-scale lot rendering, and a breakdown of value composition per property.
Six vintages of history
Estimates from 2021 through 2026 for every property, tracing how each valuation evolved across assessment-roll vintages.
Portfolio valuation
Aggregate up to 40 properties into a single portfolio view with a consolidated multi-page PDF report.
Fully vectorial PDF reports
Standard (3 pages), bank-grade professional (6 pages), portfolio, and provincial statistical reports — 100% vector output with embedded fonts via pdfkit.
Law 25 compliant
Quebec privacy-law compliance, a cookie-consent selector, and the complete public methodology embedded in the product.
How It Works
Open-data ingestion
Six vintages of Quebec's georeferenced assessment rolls (MAMH, 2021–2026) — roughly 3.7M units per vintage, 22,150,285 observations in total.
Spatial fusion
Sales are matched to assessment units via XY join in EPSG:32198 — kNN k=25 within 200 m plus value-based join within 500 m — achieving 99.88% matches at 0.6 m median distance.
Hedonic model
LightGBM on log(price) with 18 variables and P10/P90 quantile heads produces 22 million pre-computed estimates across all vintages.
Comparables engine
Candidate sales within an adaptive 2.2–28 km radius are filtered by type and size, adjusted for market, size, and age, then combined by Gaussian-weighted median.
Fusion and confidence
The final estimate blends 65% hedonic model with 35% comparables; comparable count, dispersion, and range width determine the A–D confidence grade.
Application layer
Next.js 16 serves search, estimation, portfolio, and report APIs over a SQLite base with FTS5, spatial indexes, and a smoothed monthly market index.
Tech Stack
Frontend / API
Data
Model pipeline
Reports & testing
Highlights
- Validated to the IAAO ratio-study standard: 0.995 median ratio on 102,943 held-out sales, plus a strict temporal test on 68,364 sales from 2026.
- Condos hit a COD of 11.9 — inside the IAAO's toughest ≤15 target band.
- Computes the total value of Quebec's residential stock — $2.01 trillion — with a ranking of the top 200 municipalities.
- Every dollar adjustment is shown: market conditions from a 3-month-smoothed $/m² index, size at 50% of the comparable's $/m² capped at ±25%, age at 0.5%/year capped at ±10%.
- All maps and property portraits are pure SVG drawn from registry data — no tiles, no external map services.
- Built entirely on open data: Quebec's MAMH property assessment rolls under an open license, with owner information redacted at the source.
Explore Vrai-Prix
Transparent property valuation for Quebec — the full source is on GitHub.