Version long-running metric contracts and append corrections

Before presenting percentages from a long-running operational analysis as decision-ready, define a versioned metric contract and an append-only correction ledger. For each metric, freeze and display the cohort window, denominator, unit of analysis, event and source inventory, proxy semantics, exclusions, evidence-coverage rate, and claim class: observed event, inferred need, automation candidate, or causal effect.

When a later source or better classifier changes a result, preserve the old value as superseded and record the exact delta mechanism. This prevents individually reasonable refinements from becoming a sequence of non-comparable values all labeled confirmed. It matters especially when metrics may influence staffing or other consequential decisions. A stable contract improves interpretation and auditability; it does not establish causal impact or eliminate source gaps.