Source hierarchy
Every number originates from a Tier-1 source. Tier-2 sources are used only to interpret a Tier-1 text, never as the origin of a figure. Tier-3 (blogs, forums, aggregators) is never cited, except clearly-labelled aggregated cost indices capped at "estimate" confidence.
Tier 1 — origin of any figure
- Statistics office
- International organisation
- Central bank
Tier 2 — interpretation only
- Aggregated index
Rules we enforce
- Headline figures: every headline datapoint must have at least one Tier-1 source, or it is left null and flagged low confidence.
- Aggregated indices: allowed, always labelled, capped at "estimate", and never the sole driver of a ranking or tool result.
- Re-verification cadence: every record is re-checked at least every 90 days (sooner for low-confidence records); an overdue high-confidence record fails our build until a human re-verifies it.
- Human gate: a record is only treated as editor-confirmed once our editor has checked it against the Tier-1 source. Records that aren't yet editor-confirmed are still published openly — but always with their full source list, the date they were last checked and a confidence badge showing how sure we are — so you can weigh the evidence yourself rather than us hiding work in progress.
What this means for you
Indicative figures, not a budget — official series only drive any ranking.
See the site-wide methodology for how this fits our overall research and verification process, or the editorial policy for who reviews it.