The difference between a number that is formatted correctly and one that a person was holding. It discards a substantial share of traffic, which is most of the gap between a $60 lead and a $20 one.
Related terms
Data append
Adding contact details to a record from a third-party database rather than collecting them from the person directly.
Exclusive leads
Lead records sold to a single buyer, ideally with no expiry on that exclusivity.
Contact rate
The share of purchased leads that reach an actual conversation with the merchant.