Kinds

primary

the page is the origin of its own numbers (a statistical agency, a journal, a filing, or a page that states its own study and sample).

secondary

at least half of the page's statistic and number claims are cited: by a link, a footnote, a source named from the grader's primary source list, or one of two page-level rules noted on the grade page.

repackaging

fewer than half of the page's statistic and number claims are cited.

content farm

the page carries three or more content-farm marks (such as no author, no date, unrelated topics, heavy ads) and under a quarter of its numbers have a link or a footnote.

unknown

the page could not be graded (robots.txt says no, the page could not be fetched, or it had too few claims).

Letters

A

the page is primary, or at least 90% of its checked claims were found on a primary page.

B

at least 70% of checked claims were found on a primary page, or at least 90% trace.

C

at least 40% of checked claims trace.

D

at least 10% of checked claims trace, or most checked claims cite a source that could not be fetched or that the site's robots.txt rules out.

F

under 10% of checked claims trace, with 3 or more claims checked.

no letter

a page that is not primary needs at least one checked claim for a letter, and a page of kind unknown gets none. An F needs 3 checked claims.

A claim is checked when the grader tried its first link: it read the page, could not fetch it, or found that the site's robots.txt rules it out. It traces when that link led to a primary page with the number, to a page on a primary-source site where the number was not found, or to another page that has the number.

The primary source list is a fixed list in the grader: 56 sites (statistical agencies, central banks, international bodies, survey houses, journals and preprint servers), the organizations behind them, and ADP's employment report.