Defense Project Budget Overruns: GAO Acquisitions Data
The US Government Accountability Office produces the most detailed open dataset on defense programme cost growth. Cumulative cost growth across the major programmes is 45% above baseline.
+45%
cumulative cost growth across the MDAP portfolio
$628B
total cost increase above original baselines
102
major defense acquisition programmes tracked (FY24)
2 years
average schedule slip across MDAPs
Headline overrun examples from GAO assessments
| Programme | Service | Cost growth vs original | Source year |
|---|---|---|---|
| F-35 Joint Strike Fighter | Joint | +82% | GAO-24 |
| Sentinel ICBM (formerly GBSD) | USAF | +81% | GAO-24, Nunn-McCurdy breach |
| Columbia-class submarine | USN | +12% | GAO-23 |
| Ford-class aircraft carrier (CVN-78) | USN | +23% | GAO-22 |
| Littoral Combat Ship | USN | +108% | GAO-15 |
| KC-46A Pegasus tanker | USAF | +33% | GAO-23 |
| V-22 Osprey | USMC | +186% | GAO historical |
Cost growth measured against original acquisition baselines, in then-year dollars from GAO Annual Assessments of Weapon Programmes.
Why defense programmes overrun
- Concurrency: Building production units while design and testing are ongoing. The F-35 is the canonical example of concurrency-driven rework.
- Requirements churn: 10-15 year programmes survive multiple administrations, doctrines, and threat assessments. The requirements baseline shifts.
- Optimism bias in original estimates: Programme advocates have an incentive to under-estimate to secure approval. This is the strategic-misrepresentation pattern Flyvbjerg identified for civilian megaprojects.
- Sole-source supply chain: Specialist subsystems often have one or two qualified suppliers. Cost competition is structurally limited.
- Nunn-McCurdy thresholds: US law requires re-certification at 15% / 25% cost growth. Programmes near these thresholds have an incentive to re-baseline rather than admit overrun, which then resets the clock.
Sources and how to cite
US Government Accountability Office (2024). Weapon Systems Annual Assessment. GAO-24-106831.
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