Tennis: singles, ATP/WTA tours
Sources and coverage
Where the matches come from, and what we know we have not read.
The data
Wikipedia, read through the MediaWiki API.
Each page carries a revision number: it is what says whether an edition changed since the last read, hence what has to be reread. 4,163 editions are tracked.
These three dates are never conflated: a source checked ten minutes ago may have published nothing for weeks.
The scope
The tournaments behind it
What feeds this ranking, and how much of each is actually in it. The count is on the matches stored, not on what we look for: tracking a competition does not mean the source has published its editions.
4 tournaments, 111,443 matches.
What we know we have not read
Gaps come from what the source does not publish: of a large draw, it does not always detail every preliminary round. They are not guessed: in a knockout tournament, every entrant but the winner loses exactly once, and an unbeaten player who did not win the tournament signals a missing match.