R6 — Every published number gets a label (what it is) and a vintage (how fresh); the Zestimate defence depends on it

Rule: Every customer-visible data-derived figure — a "homes near transit," an "estimated savings," a "rate," an "availability count" — gets two visible accompaniments: (a) a label stating what the number is (an estimate, a model output, an in-stock count as of when); (b) a vintage (the date / cadence at which it was last computed).

Why: Zillow Zestimate published error rates — ~1.9% on-market, ~7.5% off-market; lawsuits; 7th Circuit 2019 sided with Zillow partly because "estimate" was clearly labelled — the legal defence that survived to the 7th Circuit was that the Zestimate was always labelled an estimate, not an appraisal. The same principle applies to every published figure ([[accuracy-risk-published-data]]). The same rule also governs customer-facing calculators (R3 — Label every published estimate as an estimate, and show its vintage prominently).

How to apply:

• Default label discipline: every number gets a one-line accompaniment (what it is + vintage).
• Stale-data alerts on the maintenance side (R5 — Budget for pipeline maintenance from day one; if the client can't commit to upkeep, rent the managed version instead of building one) — if the data is older than the published cadence, show that.
• Apply the same discipline to ACS-derived figures (ACS 5-Year Estimates carry margins of error that produce "false positives" in small/rural areas if ignored) — publish the MOE.