The weekly close is the moment an AI visibility index locks in the week's rankings — the fixed reference point that all movement is measured against.
Markets close daily; AI rankings close weekly. Once the week's recommendation queries are recorded and scored across every model, the standings post as that week's close. The next run measures against it: every ↑ and ↓ on the board means "versus last close".
A fixed close keeps the record honest. Without one, a ranking can be quietly re-shuffled at any time and "movement" becomes unfalsifiable. With one, every position is a dated, citable fact.