Changing a definition that two years of reports were built on
The company decides that its headline retention metric should exclude a customer segment it has always included. The decision is correct and final. Two years of published figures, several external filings and every trend chart in the company were computed under the old definition.
What you would do first
Answer before revealing anything. The value of the exercise is entirely in committing to a diagnosis you can be wrong about.
- 1Establish who consumed the old figure and where: internal dashboards, board packs, external filings. The external ones constrain everything that follows.
- 2Compute both definitions over the full history so the size and shape of the difference is known before any decision about restatement.
- 3Decide with the accountable business owner whether history is restated, dual-published, or left under the old definition with a boundary.
- 4Find every implementation of the metric, including the ones that bypass the definition layer, because a partial migration produces a period where both are live.
What is actually going on
The trap
The fix that looks right. Read it even if you got the answer — especially then.
Apply the new definition to all history so the trend is continuous and nobody is confused by a step. Every previously published figure silently changes, the filed numbers can no longer be reproduced from the platform, and the discontinuity that was a fact about the business has been replaced by a chart that is wrong everywhere.