Sunk-cost discipline
Prior investment increases the tendency to continue a course of action regardless of its prospects. The discipline holds that what has been spent argues for nothing, and that only the value remaining against the cost remaining, compared with the alternatives, counts. It governs half-done migrations, championed bets and legacy systems.
Evidence grade: research Peer-reviewed or large-sample empirical work supports it.
Use it when
Any "we've come too far to stop" argument, especially when the bet is your own.
Where it stops working
The opposite error also exists, which is abandoning sound long bets at the first fashionable alternative. Changed fundamentals justify switching; novelty does not.
Where the standard uses it
- SV-3RoadmappingBalancing product delivery against platform and quality investment.
- SV-4Engineering economicsHeadcount, budget, cost of delivery, vendors, and build/buy/AI decisions.
Sources
- Hal R. Arkes and Catherine Blumer. The Psychology of Sunk Cost. Organizational Behavior and Human Decision Processes, 35(1), 124–140, 1985. In the bibliography
Used alongside it
- Build, buy, or AI service practice
- Core versus context practice
- Explicit capacity allocation practice
- Headcount as investment practice
- Staged bets and checkpoints practice
- The three horizons practice
Cite this model
Chicago, BibTeX and licence →Engineering Management Academy. (2026). Sunk-cost discipline. In Engineering Management Academy Body of Knowledge (Version 3.1, TEC.sunk-cost-discipline). https://www.engineeringmanagement.academy/body-of-knowledge/techniques/sunk-cost-discipline