Methodology
Durability Score (Ds)
A composite score at the brand × category × market level. Five indicators, public weighting, validated against Stiftung Warentest and Consumer Reports.
Ds v2.0 · continuously updated
Core principles
Independence
Ratings are not based on payments by manufacturers or retailers. No financial relationship may influence a result.
Transparency
Data sources, weighting, and calculation method are published. Anyone may challenge the methodology.
Reproducibility
Each release carries a methodology version number. Code and data are public on GitHub and Zenodo.
Currency
Ratings are reviewed annually; a weighting change causing a shift of 2+ positions triggers a 30-day public consultation.
Five Durability Score indicators
The final Ds is a weighted average of five indicators. Each rating carries an evidence grade A–D.
Consumer experience
30 %Weighted average of recommendations across platforms, weighted by the number of verified reviews.
Sources: Heureka, Amazon, Ceneo, MediaMarkt
Repairability
25 %Composite of iFixit score, French Indice de Réparabilité, Stiftung Warentest / dTest repair tests, and spare-parts availability.
Sources: iFixit, indicereparabilite.fr, Stiftung Warentest, dTest, manufacturer parts catalogues
Quality stability over time
20 %Slope of a brand's monthly ratings over time, normalised to [0, 1]. Declining ratings over time signals higher obsolescence risk.
Sources: Longitudinal scrapes of review platforms
Observed in-use lifespan
15 %Presence of products on the secondhand market years after launch. Brands whose products survive longer score higher.
Sources: Bazoš, Aukro, Re-Use centre data; Stiftung Warentest / dTest endurance tests
Warranty & complaint signal
10 %Proxy complaint rate from the internal QualityDB and a partner e-shop.
Sources: Internal QualityDB; partner e-shop (under NDA)
Calibration: Spearman ρ > 0.5 against Fnac Darty Baromètre du SAV (primary) and Consumer Reports (secondary), pre-registered before each release.
Derived metrics
Quality Coverage Ratio
Share of a brand's portfolio that meets the minimum quality threshold. Distinguishes premium brands from those with just a few good models.
Brand Consistency Index
Intra-class correlation of Ds across markets. High BCI = the brand pursues a consistent quality strategy. Low BCI = markedly different quality by market.
Obsolescence Risk Score
Derived metric 0–100 computed by the ODA algorithm (PELT change-point detection) from longitudinal review trajectories. Signals whether managed obsolescence is occurring.
Evidence grades A–D
Every rating carries a visible evidence grade so readers cannot mistake a weak signal for a verdict. Ratings of C or D are published with a warning and may not be used in headlines or comparison tables.
Multiple independent laboratory tests + repairability data + warranty/complaint statistics + consumer survey, all consistent.
Multiple independent sources in agreement, but limited scope or sample size.
One independent source or anecdotal data. The result is preliminary.
Data unavailable or inconsistent. Ratings are not published in headlines.
Data sources and partners
Stiftung Warentest (DE)
Independent foundation, ~200 comparative tests per year, endurance tests, reference for calibrating R and O
Which? (UK)
Consumer association, ICRT member; longitudinal reliability surveys, calibration of T
Consumer Reports (US)
Non-profit ICRT member; annual survey with hundreds of thousands of households; primary benchmark for US-active brands
dTest (CZ)
Czech consumer association, ICRT member; laboratory tests and consumer context for the Czech market
iFixit.com
Repair community; repairability scores, teardown documentation, parts availability — direct input to R
Indice de Réparabilité (FR)
Mandatory government index since 2021; largest source of structured repairability scores in the EU — direct input to R
Fnac Darty Baromètre du SAV
Retailer service report; primary calibration benchmark for European brands
EU EPREL database
EU energy register; authoritative model-level metadata; taxonomic foundation
QualityDB (internal)
Proprietary longitudinal architecture (DCT/FMT layers, PELT ODA); basis for W and T indicators
Secondhand Deal Finder (internal)
Secondary-market data from Bazoš, Sbazar, Vinted; lifespan proxy for the O indicator
Existing research base
N = 408 respondents
Czech consumer survey
15 appliance brands, 6 quality dimensions, five-item planned-obsolescence belief scale (α = 0.896), expected lifespan of washing machine, refrigerator, dishwasher and dryer.
2,106,167 listings
Amazon marketplace dataset
Analysis of rating distributions, review concentration (Gini, Lorenz) and Bayesian-shrunk quality estimates; submitted to Journal of Big Data.
DCT/FMT layers, PELT ODA
QualityDB longitudinal architecture
Obsolescence-detection algorithm based on change-point detection in time series; basis for the ORS metric and MSK 2025 grant applications.
Interval-censored Weibull MLE
Manuscript: appliance lifespan
Estimation of real lifespan for washing machines, refrigerators, dishwashers and dryers; benchmarked against EU Ecodesign reference values.
Rating updates
Every rating is reviewed annually. A weighting change causing a shift of 2+ positions triggers a 30-day public consultation. The review date is visible on each record.
Challenge a rating
Manufacturers and directly affected parties may submit a rebuttal within 30 days of publication (max. 800 words). Rebuttals are published alongside the report — they never confer veto rights.
Report an error or submit a rebuttalThis is the abbreviated web version of the Ds v2.0 methodology. The full specification — formulae, code, validation results and data schema — is published on GitHub and Zenodo with each rating release.
Transparency and funding