What is Data decay?

Data decay is the steady loss of accuracy in a contact list as businesses close, move, rebrand, change phone numbers and close mailboxes.

Also called: list decay, data freshness.

Every field in a lead list goes stale at its own pace. Emails go first: a mailbox closes when an employee leaves or a business changes provider. Websites lapse when a domain is not renewed. Phone numbers, addresses and names change less often but still change, and small local businesses open and close constantly.

Decay is why the date of a check matters as much as its result. An address that passed SMTP verification months ago is an address that passed months ago; it says little about today. A large downloaded database that is not re-checked before use is where high bounce rates come from.

The defence is to pull records close to when you will use them, re-verify anything older than a few weeks before a campaign, and keep the source and check date on each record so stale fields are visible; see B2B data enrichment.

A site that no longer loads is decay you can see: the website down checker tests any site, and the State of Local Business Websites 2026 report counts how many listed sites fail to load.