GeoRank Data Methodology

The ERA5 bias problem

ERA5 is ECMWF's flagship reanalysis dataset — the most comprehensive global atmospheric record available. However, ERA5's raw sunshine duration values overestimate actual sunshine hours by a systematic margin that varies by cloudiness regime:

• Clear, dry climates (e.g. deserts, Mediterranean): +5–16% overestimation
• Mid-latitude temperate climates: +20–40% overestimation
• High-latitude, cloudy climates (e.g. northwest Europe): +40–73% overestimation

This means raw ERA5 makes Bergen, Glasgow, and Reykjavik appear substantially sunnier than they are in practice. Without correction, rankings of "cloudy" cities are meaningless.

Correction formula

GeoRank applies a linear correction derived from comparing ERA5 values against WMO ground-station observations at 56 reference locations worldwide:

R² = 0.82 · n = 56 stations · Residual RMSE ≈ 180 hr/yr

The formula reduces ERA5's systematic overestimation in cloudy regions while preserving relative differences between sunny and cloudy climates. At 0.5° resolution this produces calibrated values that track observed sunshine hours within ±8% for most locations.

IDW spatial interpolation

After applying the correction formula globally, residual errors at non-station locations are reduced using Inverse Distance Weighting (IDW) — a spatial interpolation technique that weights nearby station corrections more heavily than distant ones. The IDW radius is tuned to 500 km, balancing spatial resolution against over-correction in data-sparse regions.

Ångström–Prescott formula

Sunshine hours are derived from solar irradiance data using the Ångström–Prescott formula, which estimates bright sunshine duration from diffuse and direct radiation ratios:

Where S = actual sunshine hours, S₀ = maximum possible sunshine hours (astronomical daylength), n/N = cloudiness fraction, a and b are empirical constants calibrated per climate zone.

Tax rates are sourced from official government publications and cross-referenced against OECD tax database and PwC Worldwide Tax Summaries. Rates reflect top marginal rates for each tax category as of the date shown below.

Tax rates on GeoRank represent marginal income tax at €50,000 equivalent annual income for a single individual, and headline statutory capital gains rates. These are not effective rates — what most people actually pay is lower once thresholds, allowances, and credits apply.

Sources and update cadence

What's excluded

• Social contributions: employer and employee social security are not included in the displayed rate. In France, Germany, or the Netherlands these add 15–25 percentage points to the effective burden.
• Municipal and regional surcharges: subnational taxes (German Kirchensteuer, Italian IRAP, US state income tax) are excluded.
• Wealth and exit taxes: not modelled.

Known limitations

• Territorial vs worldwide taxation: the distinction (Georgia, Panama, Costa Rica tax only locally-sourced income) is noted per-country but not always surfaced in the headline rate comparison.
• Special regimes: Portugal NHR/NHR 2.0, Cyprus non-dom, Georgia Virtual Zone, Malta global residence — shown separately where available.
• Crypto treatment: changes frequently and may lag current law by 1–2 quarters. Treat crypto figures as indicative only.

The monthly cost estimate represents a single-person baseline: 1-bedroom apartment in a city-centre or near-centre neighbourhood, standard utilities, weekly groceries, local public transport, and dining out approximately three times per week. It is not a minimum-cost figure and not a luxury figure.

Sources

What's excluded

• International health insurance: typically $100–300/mo depending on age and coverage
• Flights home: highly variable, not modelled
• Car ownership or rental
• Language school or visa fees

Known limitations

• Expat-price skew: Numbeo contributors are disproportionately Western expats. Reported rents and restaurant prices reflect the expat-visible market, not the local market. In cities like Tbilisi, Chiang Mai, or Medellín, a local-market lifestyle costs 20–40% less than our figures suggest.
• Neighbourhood variation: one figure per city masks large within-city variance. A listing in Lisbon's Príncipe Real costs twice a listing in Mouraria.
• Currency volatility: USD-denominated figures are updated quarterly but may lag a sharp devaluation.

GeoRank provides calibrated estimates of annual sunshine hours derived from reanalysis datasets and ground-station correction. Accuracy characteristics:

• Most locations: within ±8% of long-run observed sunshine hours
• High-altitude locations: ±12–15% (elevation correction not yet applied)
• Coastal microclimates: ±10–20% (0.5° cells average over sea/land boundaries)
• Urban heat islands: not modelled; values represent the grid cell, not city centre

Cost of living estimates are illustrative only. They represent a reasonable ballpark for a single person renting a one-bedroom apartment in a mid-tier neighbourhood, eating out 3–4 times per week, and maintaining a moderate lifestyle. Actual costs depend heavily on lifestyle, neighbourhood, and individual spending.

Tax rates are top marginal rates. Effective rates (what most people actually pay) are typically lower. Tax treaties, special regimes, and tax-free thresholds are not included in the headline figures unless explicitly noted.

Monthly mean 2-metre air temperature is derived from ERA5 reanalysis (Copernicus Climate Data Store, dataset reanalysis-era5-single-levels-monthly-means) on a 0.25° native grid, aggregated to a 0.5° resolution for the global map and to a 30-year climatology (1991–2020).

• Typical accuracy: ±1–2 °C against ground stations in well-instrumented regions
• Urban heat islands: not modelled — values represent the 0.5° grid cell, which can underestimate dense-city centres by 1–3 °C in summer
• Coastal grid cells: blend sea and land; expect smoother seasonal swings than nearby inland weather stations
• High elevation: ERA5 surface elevation differs from real terrain; expect ±2–3 °C error in mountain regions

SourceERA5 · Copernicus CDS

Climatology1991–2020 · monthly means

Total precipitation comes from ERA5 monthly means, corrected against rain-gauge observations where available. Annual rainy days are estimated from the daily-mean precipitation rate via a Gamma-distributed wet-day model:

• Typical accuracy: ±12% on annual totals in well-gauged regions
• Orographic effects: ERA5 underestimates rain shadows and windward enhancement at high resolution; expect ±25% in mountainous coastal terrain
• Tropical convective regimes: the wet-day model assumes Gamma-distributed daily totals; in monsoon zones, real day counts can run higher than estimated
• Snow vs. rain: total precipitation includes both; the rainy-day count is not snow-separated

SourceERA5 + rain-gauge calibration

Resolution0.25° native · 0.5° aggregated

Annual-mean surface PM2.5 concentration (µg/m³) is sourced from the Copernicus Atmosphere Monitoring Service (CAMS) global reanalysis EAC4 on a ~10 km grid. Tier colors map to WHO air-quality guideline thresholds:

• < 5 µg/m³ — meets WHO 2021 annual guideline (best)
• 5–10 µg/m³ — WHO interim target 4
• 10–25 µg/m³ — interim targets 3 → 2
• 25–35 µg/m³ — interim target 1
• > 35 µg/m³ — exceeds all WHO interim targets

CAMS reanalysis is a global model assimilating satellite retrievals and surface measurements; it represents the regional grid cell, not a specific street-level monitor. Expect higher real-world values near busy roads, industrial sites, or seasonal biomass-burning events.

SourceCopernicus CAMS · EAC4 reanalysis

Threshold referenceWHO 2021 AQ guidelines

Country safety scores come from the Global Peace Index 2025, published by the Institute for Economics & Peace. The index covers 163 countries and scores each across 23 indicators grouped into three domains:

• Societal safety & security — homicide, incarceration, perceived criminality, political stability, violent demonstrations
• Ongoing domestic & international conflict — deaths from internal/external conflict, relations with neighbours
• Militarisation — military expenditure, armed services personnel, weapons imports/exports, nuclear capability

The composite GPI score is normalised to a 1.0 (most peaceful) to 5.0 (least peaceful) scale, and updated annually. It is an assessment of current-year state, not a predictive model — countries can shift quickly in response to political events, and short-term incidents may not yet be reflected.

SourceGlobal Peace Index 2025 · IEP

Coverage163 countries · 23 indicators

To reference GeoRank data in academic, professional, or editorial contexts:

Primary upstream data sources:

• Hersbach et al. (2020). ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society.
• NASA POWER Project. Prediction of Worldwide Energy Resources. NASA Langley Research Center.
• ECMWF (European Centre for Medium-Range Weather Forecasts). ERA5 hourly data on single levels.

GeoRank methodology and the calibrated sunshine, temperature, and rainfall datasets are licensed under Creative Commons Attribution 4.0 International (CC-BY-4.0). You may use, share, and adapt with attribution — see Cite this data for the recommended citation format.

Tax, cost-of-living, air-quality, and safety data are derived from third-party sources (OECD, PwC, KPMG, Numbeo, Copernicus Atmosphere Monitoring Service, Institute for Economics & Peace) and are subject to their respective licenses. Consult each source for redistribution rights.