TDRF

Target Date Retreat Factor - a measure of the change in schedule for a project over time.

Schedules often "slip". When the slip is enough to keep the expected project delivery about the same distance in the future, then the TDRF is 1.0 (as in "FHP will be delivered in 18 months", that was the schedule in 1978, 1979 and 1980 - see _The Soul of a New Machine_).

The Boeing 787 Dreamliner seems to have a TDRF of about 0.5

A project that is on schedule, and stays on schedule would have a TDRF of 0.0.

It is theoretically possible for a project to have a negative TDRF. This would indicate a project that was delivered early.