Freshness & series rot

How current a number is. Public data publishes on a fixed schedule, so every figure ages between releases — and presenting a stale value as if it were today's reading is its own kind of lie. Series rot is a feed that quietly stops updating, leaving a last value that looks fine but isn't current.

Why it matters

A number's age matters as much as its value: an accurate figure read months late can be just as wrong as a bad one. The Cost Index stores every value's vintage, weighs each reading against its source's own cadence, and watches for series rot — a feed that stalls. A rotting or overdue series is flagged or dropped to absent with the reason, never shown as if it were today's number.

Frequently asked

What does data freshness mean?

Freshness is how current a number is — when it was last updated, not just what it says. Most public data publishes on a fixed schedule (a monthly index, a weekly report), so between releases every figure is aging. A value can be perfectly accurate the day it posts and quietly out of date a few weeks later. Reading the value without reading its date is how an old number gets mistaken for today's.

What is series rot?

Series rot is when a data feed you depend on quietly stops updating — a report that gets discontinued, a series that's suppressed, or a source that just goes silent without announcing it. The danger is that the last value sits there looking fine, so a stale figure can pass as current indefinitely unless something is watching for the stall. Old is not the same as overdue: a monthly number a month old is fine; a monthly number that skipped its release is rotting.

How does the Muntin Cost Index handle freshness and series rot?

Every value stores its vintage — the date of the reading behind it. A freshness heartbeat reports the oldest reading and turns a persistent stall red on the weekly refresh, and each value is weighed against its source's own cadence, so a print that falls overdue for the rhythm its source normally keeps is marked down in confidence until it refreshes. If a series is discontinued or goes silent, the ingredient becomes absent with the reason — never a silent zero, and never a frozen last value pretending to be current.

How do you know if data is out of date?

Check its vintage — the date of the reading, not just the value — against how often the source normally publishes. A monthly series a month old is fine; one that skipped its release is overdue. The Cost Index stores every value's vintage, weighs it against the source's own cadence, and flags or drops a series that quietly stalls instead of showing a stale number as current.