A customer crossing a segment boundary between periods, so the norm it is measured against changes. Reported as its own list with the old and new norm side by side, so the gap that appears is explained.
A customer that grew past a boundary can gain a four-product gap overnight with nothing else changing. Without the migration list, the gap list shows a finding from nowhere.
Reassign segments on a fixed cadence from period-end figures. Monthly reassignment on a volatile measure makes customers oscillate.
Customers that crossed a segment boundary between periods, listed with the norm they were measured against before and after.
A customer grew from 45 to 60 sites and moved band. Its gap at norm rose from $20,000 to $95,000 without its buying changing, because its peers are now larger.
A jump in a customer's gap read as a change in the customer.