When to use it
Use it to detect persistent forecast drift before a deadline is missed.
A stable forecast can conceal poor progress measures; the picture does not identify a root cause.
Apply it
Compare forecasts for the same milestone and calendar; a positive drift means a later forecast.
- Retain each status date and the forecast finish recorded then.
- Plot forecast finish against status date without replacing old estimates.
- Investigate drift, changed assumptions and the action needed.
An example in practice
A service-launch forecast moves later at each review even though task reports remain green. Ask for evidence behind remaining durations and dependencies.
Source & credit
Common scheduling practice. The critical-path method is associated with James E. Kelley Jr. and Morgan R. Walker; their 1959 paper is the historical reference.
GAO: Schedule Assessment Guide
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