Methodology & Data Notes
How New River Analytics calculates every number — and what it can and can't tell you. For the assessor accountability scores specifically, see Accountability Methodology & Data.
Coverage & data sources
New River Analytics covers all 55 West Virginia counties (~1.5 million parcels). Parcel and assessment attributes come from county assessor records and the WV GIS Technical Center; current appraised values are tax year 2025 (snapshot Jun 16, 2026).
- Appraised value roll — the 100% appraised value the assessor has on the books (the 60% assessed value used for tax is derived from it). 20+ years of value history (2000–2025) back the trend and reappraisal-cadence tools.
- Arms-length sales — recorded deed sales (validity-coded), the basis for the sales-ratio studies, comparable sales, and the residential market model.
Time-adjusting sales
When sales from different years are compared, each price is adjusted to a common year using a published Bailey–Muth–Nourse repeat-sales index ("WV Case-Shiller") built from pairs of resales statewide. Comparing un-adjusted prices across a rising market is the single most common ratio-study error, so it is applied everywhere a cross-year sale is used.
Market estimate (AVM)
For improved residential parcels we publish a screening-grade automated market estimate (a gradient-boosted model trained on arms-length sales and public-record features: size, age, location/adjacency, prior sale). It is calibrated to recent sales and ships with an 80% likely-range. It is screening-grade, not a certified appraisal.
Vacant land and commercial parcels are not modeled — WV assessors value those accurately per parcel, and the honest add is transparency, so we show comparable recent sales (a market range) instead of a model verdict.
Comparable properties
Comparables are real nearby arms-length sales of similar parcels (same county, same property class, a size band, within a distance cap, time-adjusted), with the assessor's similarity factors used to rank closeness when sale comparables are thin.
- Improved: living area, year built, acreage, grade, district.
- Vacant land: acreage band + land use.
Sales-ratio study & uniformity (IAAO)
A direct, time-matched ratio study: for each arms-length sale, ratio = appraised value in the sale year ÷ sale price. From the ratios we report the standard IAAO measures:
- Median ratio — level of assessment (WV targets ~100% of market; it usually runs below, from reappraisal lag + a rising market).
- COD — uniformity (dispersion of the ratios; IAAO target ≤15 for improved residential). Lower = parcels assessed more evenly relative to each other.
- PRD / PRB — vertical equity. Regressive (PRD >1.03 / PRB negative) means lower-value homes are assessed at a higher ratio than high-value homes.
The Accountability tools apply these per county and per elected assessor, with pass/warn/fail flags and confidence tiers — see Accountability Methodology for the grading rules.
"Is my assessment fair?"
The homeowner verdict is about uniformity, not absolute over-assessment: it compares your parcel's assessment-to-market ratio to the median of nearby comparable parcels. Because WV assessments broadly run below market, the meaningful question is whether you're assessed high relative to your neighbors — the pattern that supports an appeal.