List age is the days or months since a list was last edited: a client added, removed or re-tiered. Lists drift from the book they describe, and the age is the simplest measure of how far. It is shown beside the list's hit rate or coverage so that a stale list with a low rate is a review, not a mystery.
Today's date minus the date a distribution list, call plan or target list was last edited.
A target list of 120 prescribers was last edited eleven months ago. Eighteen of the territory's top fifty prescribers by current volume are not on it.
Lists treated as settled. The market moves and the list describes last year.