Retired label. What is now Tier 2, Multiple sources.
Corroborated meant two or more genuinely independent sources state the same thing. That is now Tier 2, Multiple sources.
The requirement has not moved: a compilation and a second compilation drawing on the first are one source wearing two hats, and they do not corroborate each other. What changed is the word. Corroborated is a term of art readers had to be taught; Multiple sources is what it always meant.
This word was retired in September 2026. It is kept as a page because it appears in dossiers published before then, in API responses until the field is removed on 31 March 2027, and in anything a reader bookmarked. Nothing about the underlying standard changed — only what we call the result.
Verified means the primary instrument was read. Corroborated means several secondary sources agree about what it says.
Compiled is one source, or several that are not independent. The line between the two grades is independence, not count.
See also evidence tier · assurance · verified · compiled · precision
min_assurance keeps working until 31 March 2027 and keeps its old values. See what we hold.