Methodology & data sources
Every number on this site traces back to a public source. This page explains where the data comes from, how often it refreshes, and how each tool calculates its results.
Data sources
- Income percentiles: World Inequality Database (wid.world), OECD, and World Bank PIP data.
- Inflation (CPI): US BLS CPI-U series (1913–present), UK ONS, OECD.
- Asset price history: Stooq historical data and CoinGecko (crypto), yearly closes, split-adjusted.
- Exchange rates: Frankfurter API (European Central Bank reference rates).
- Average wages & price levels: OECD and national statistics offices.
- Billionaire net worth: a small list compiled manually from Forbes, updated quarterly.
How fresh is the data?
Market prices and exchange rates refresh automatically every day; monthly series like CPI refresh when their source publishes. Each tool shows a "Data updated" date — currently 2026-07-24 for market data. If a source is temporarily unavailable we keep the last good value rather than guessing.
Per-tool calculation notes
As each tool launches, its exact formula and assumptions are documented here and in the "How this is calculated" section on the tool page itself.
Limitations
These tools are simplified models for curiosity and education. Global income comparisons use purchasing-power adjustments that carry real uncertainty; historical returns ignore taxes, fees and dividends unless stated. Nothing on this site is financial advice.