Each country from its first published month to last month. A full year is one green block; a year with a gap opens into its twelve months, so you can see exactly which are missing. Nothing before a country's first figure counts as a gap.
GET /v1/gaps or GET /v1/gaps?country=VNEvery red month is on our work list. We go back to the publisher, then to a second official source that counts the same thing, and check the two agree on the months they share before anything is stored.
Some months were never released: a survey paused, a table that skips a season. Those are grey, recorded as the source's own gap, and never filled with an estimate.
If you know where a missing month is published, tell us and it is checked within a day. Every fill is listed in the changelog with the date it arrived.