A drop after a change is not proof the change caused the drop

The most requested plate in this practice is the one that would prove a new arrangement damaged usage. Visitors arrive with the date of the change already circled. They want the line to break on that date and nowhere else.

Sometimes it does. More often the drop began two days earlier, or the change was logged on Thursday while the latch was actually moved on Tuesday, or a public holiday emptied the building on the same morning.

In the sitting we place two plates side by side: the configuration state by day, and the usage count by day. Where they share a date, we say they share a date. Where a story would require a hidden mechanism, we stop. If you need a cause, that is a different kind of work, and we will not sell it as a drawing.

The mild unhappiness this causes is familiar. A director in Didube told us the pack was “incomplete” because it would not blame the new night mode. The night mode had been on for eleven days. Usage had been falling for twenty. Both facts are still on the plates in our archive.