Reading a contribution stack without overclaiming
Contribution margin is a period arithmetic. It is not a verdict on next quarter, and the chart should not pretend otherwise.
A stack that runs from revenue down through named variable costs is a record of the period you closed. Annotate it with the cost names you actually booked: freight, contract labor, materials — not a generic “COGS blob.”
What it cannot do is tell a board that the same stack will repeat. Volume, mix, and a single supplier invoice can move the next period without any change in “strategy.”
We print the period name in the chart title, not in a caption someone might crop. If a slide leaves the room, the date should still be on the drawing.
When a line is an estimate rather than a booked cost, mark it. Unmarked estimates are how a review turns into an argument about whether the chart is “real.”