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Government Project Budget Overruns: Why Public Sector Projects Always Cost More

Public projects have more scrutiny, oversight, and audit than private ones -- yet they consistently overrun more. Understanding why requires understanding the political economy of project approval.

70%+
of US federal projects overrun budget
McKinsey 2021
53%
average federal project overrun
McKinsey
£100B+
HS2 total cost estimate (was £37.5B)
UK Parliament 2024

The Real Explanation: Strategic Misrepresentation

Professor Bent Flyvbjerg of Oxford's Said Business School provides the most honest explanation for government project overruns: many initial budgets are not genuine estimates. They are political constructs designed to be low enough to secure approval.

The mechanism is straightforward. A project champion -- a politician, a promoter, a contractor -- knows that the project would not be approved at its realistic cost. So the initial estimate is kept deliberately low. The project is approved and funded. Once construction begins, cancellation becomes politically and financially catastrophic: sunk costs, contractor commitments, and political embarrassment make it worse to stop than to continue spending. The project is "too big to fail."

This is not incompetence -- it is rational self-interest for the individuals involved. The project promoter secures funding and careers are made. The overrun comes years later, long after the initial decision-makers have moved on. Flyvbjerg documents this pattern across hundreds of infrastructure projects spanning 20 countries.

Reference: Flyvbjerg, B. (2009). "Survival of the Unfittest: Why the Worst Infrastructure Gets Built -- and What We Can Do About It." Oxford Review of Economic Policy, 25(3), 344-367.


UK Government Project Overruns

ProjectOriginal EstimateLatest CostOverrunStatus
HS2 Phase 1£37.5B£67B+79%+In construction
Crossrail (Elizabeth Line)£14.8B£18.9B28%Complete (2023)
Edinburgh Trams£375M£1.1B193%Complete (Phase 1, 2014)
Universal Credit (DWP)£2.4B£6B+150%+Ongoing -- 10+ years late
NHS Patient Records (NPfIT)£6.4B£10B+56%+Cancelled 2011

US Federal Project Overruns

ProjectOriginal BudgetActual / Latest EstimateOverrun
F-35 Joint Strike Fighter$233B (2001)$400B+72%+
Healthcare.gov$93.7M$1.7B+1,700%+
Boston Big Dig (Federal Highway)$2.8B$14.8B429%
FBI Virtual Case File$170M$170M spent, nothing delivered100% waste
James Webb Space Telescope (NASA)$500M$10B1,900%

Frequently Asked Questions

Why do government projects always go over budget?

Government projects overrun for structural reasons beyond poor management. Flyvbjerg's theory of strategic misrepresentation explains that politicians and project promoters deliberately understate costs to secure approval. Once funded and started, cancellation is politically worse than overspending. Procurement rules that favour the lowest bid over the best plan compound the problem.

What is the UK government's record on major project costs?

The Infrastructure and Projects Authority (IPA) annual report consistently shows the majority of major UK projects are late and over budget. HS2 Phase 1: from £37.5B to £67B+. Crossrail: from £14.8B to £19B. Universal Credit: from £2.4B to £6B+. Edinburgh Trams: from £375M to £1.1B. The pattern is consistent across sectors.

What is the GAO High Risk List?

The US Government Accountability Office (GAO) maintains a biennial "High Risk List" of federal programs with persistent cost, schedule, or management problems. Defence acquisition programmes consistently appear. Being on the High Risk List signals systemic governance failure. The GAO's reports are publicly available and are the primary source for US federal project overrun data.

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