When to use it
Use it for a consistently measured backlog over time.
When to be cautious
A straight trend line is not a promise; changed scope and work-size variation can dominate it.
Apply it
Remaining scope = total current scope − completed scope
Keep scope changes separate from delivery progress. A straight-line extension assumes a continuing rate and stable scope.
- Define completion and a stable counting unit.
- Retain historical totals and show scope additions separately.
- Compare rate-based scenarios with dependencies and remaining work.
An example in practice
A burnup shows steady completion while the total scope rises faster. Discuss scope decisions rather than blaming the delivery rate.
Source & credit
Standard estimating practice; the cited guide documents use rather than claiming invention.
GAO: Cost Estimating and Assessment Guide
This explanation and example are independently written. The source is a reading reference; linking it does not grant permission to reuse its text, figures or assessments.