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Five things you should know about cost overrun

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  • Flyvbjerg, Bent
  • Ansar, Atif
  • Budzier, Alexander
  • Buhl, Søren
  • Cantarelli, Chantal
  • Garbuio, Massimo
  • Glenting, Carsten
  • Holm, Mette Skamris
  • Lovallo, Dan
  • Lunn, Daniel
  • Molin, Eric
  • Rønnest, Arne
  • Stewart, Allison
  • van Wee, Bert

Abstract

This paper gives an overview of good and bad practice for understanding and curbing cost overrun in large capital investment projects, with a critique of Love and Ahiaga-Dagbui (2018) as point of departure. Good practice entails: (a) Consistent definition and measurement of overrun; in contrast to mixing inconsistent baselines, price levels, etc. (b) Data collection that includes all valid and reliable data; as opposed to including idiosyncratically sampled data, data with removed outliers, non-valid data from consultancies, etc. (c) Recognition that cost overrun is systemically fat-tailed; in contrast to understanding overrun in terms of error and randomness. (d) Acknowledgment that the root cause of cost overrun is behavioral bias; in contrast to explanations in terms of scope changes, complexity, etc. (e) De-biasing cost estimates with reference class forecasting or similar methods based in behavioral science; as opposed to conventional methods of estimation, with their century-long track record of inaccuracy and systemic bias. Bad practice is characterized by violating at least one of these five points. Love and Ahiaga-Dagbui violate all five. In so doing, they produce an exceptionally useful and comprehensive catalog of the many pitfalls that exist, and must be avoided, for properly understanding and curbing cost overrun.

Suggested Citation

  • Flyvbjerg, Bent & Ansar, Atif & Budzier, Alexander & Buhl, Søren & Cantarelli, Chantal & Garbuio, Massimo & Glenting, Carsten & Holm, Mette Skamris & Lovallo, Dan & Lunn, Daniel & Molin, Eric & Rønnes, 2018. "Five things you should know about cost overrun," Transportation Research Part A: Policy and Practice, Elsevier, vol. 118(C), pages 174-190.
    • Handle: RePEc:eee:transa:v:118:y:2018:i:c:p:174-190
    DOI: 10.1016/j.tra.2018.07.013
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    Cited by:

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    3. Cavalieri, Marina & Cristaudo, Rossana & Guccio, Calogero, 2019. "On the magnitude of cost overruns throughout the project life-cycle: An assessment for the Italian transport infrastructure projects," Transport Policy, Elsevier, vol. 79(C), pages 21-36.
    4. Kopel, Michael & Ramani, Vinay, 2024. "The bright side of the planning fallacy in distribution channels," European Journal of Operational Research, Elsevier, vol. 314(2), pages 540-551.
    5. Love, Peter E.D. & Ika, Lavagnon A. & Ahiaga-Dagbui, Dominic D., 2019. "On de-bunking ‘fake news’ in a post truth era: Why does the Planning Fallacy explanation for cost overruns fall short?," Transportation Research Part A: Policy and Practice, Elsevier, vol. 126(C), pages 397-408.
    6. Ivona Ivić & Anita Cerić, 2023. "Risks Caused by Information Asymmetry in Construction Projects: A Systematic Literature Review," Sustainability, MDPI, vol. 15(13), pages 1-25, June.
    7. Penyalver, Domingo & Turró, Mateu & Williamson, John B., 2019. "Measuring the value for money of transport infrastructure procurement; an intergenerational approach," Transportation Research Part A: Policy and Practice, Elsevier, vol. 119(C), pages 238-254.
    8. Jenkins, G. & Olasehinde-Williams, G. & Baurzhan, S., 2022. "Is there a net economic loss from employing reference class forecasting in the appraisal of hydropower projects?," Renewable and Sustainable Energy Reviews, Elsevier, vol. 159(C).
    9. Lozano, Jorge-Mario & Zuluaga, Santiago & Sánchez-Silva, Mauricio, 2020. "Developing flexible management strategies in infrastructure: The sequential expansion problem for infrastructure analysis (SEPIA)," Reliability Engineering and System Safety, Elsevier, vol. 200(C).
    10. Ginés de Rus & Javier Campos & Daniel Graham & M. Pilar Socorro & Jorge Valido, 2020. "Evaluación Económica de Proyectos y Políticas de Transporte: Metodología y Aplicaciones. Parte 1: Metodología para el análisis coste-beneficio de proyectos y políticas de transporte," Working Papers 2020-11, FEDEA.
    11. Flyvbjerg, Bent & Bester, Dirk W., 2021. "The Cost-Benefit Fallacy: Why Cost-Benefit Analysis Is Broken and How to Fix It," Journal of Benefit-Cost Analysis, Cambridge University Press, vol. 12(3), pages 395-419, October.
    12. Dorota Kuchta & Paolo Canonico & Vincenza Capone & Guido Capaldo, 2023. "Uncertainty in the Planning Phase of Public Projects—Its Scope, Consequences, and Possible Remedies," Administrative Sciences, MDPI, vol. 13(6), pages 1-17, June.
    13. Love, Peter E.D. & Ika, Lavagnon A., 2021. "The ‘context’ of transport project cost performance: Insights from contract award to final construction costs," Research in Transportation Economics, Elsevier, vol. 90(C).
    14. Antonio Estache & Renaud Foucart & Tomas Serebrisky, 2022. "When can Lotteries improve Public Procurement Processes?," Working Papers ECARES 2022-22, ULB -- Universite Libre de Bruxelles.
    15. Jelena M. Andrić & Shuangyu Lin & Yuan Cheng & Bin Sun, 2024. "Determining Cost and Causes of Overruns in Infrastructure Projects in South Asia," Sustainability, MDPI, vol. 16(24), pages 1-22, December.
    16. Giuliano Marella & Valentina Antoniucci, 2019. "Time Overrun in Public Works—Evidence from North-East Italy," Sustainability, MDPI, vol. 11(24), pages 1-17, December.
    17. Isaac Akomea-Frimpong & Xiaohua Jin & Robert Osei-Kyei, 2022. "Mapping Studies on Sustainability in the Performance Measurement of Public-Private Partnership Projects: A Systematic Review," Sustainability, MDPI, vol. 14(12), pages 1-20, June.
    18. Bent Flyvbjerg & Alexander Budzier & Daniel Lunn, 2021. "Regression to the tail: Why the Olympics blow up," Environment and Planning A, , vol. 53(2), pages 233-260, March.
    19. Temitope Seun Omotayo & Bankole Awuzie & Valerie Kenechukwu Obi & Saheed Ajayi & Lovelin Ifeoma Obi & Oluyomi Osobajo & Adekunle Oke, 2022. "The System Dynamics Analysis of Cost Overrun Causations in UK Rail Projects in a COVID-19 Epidemic Era," SAGE Open, , vol. 12(2), pages 21582440221, May.
    20. Jarosław Górecki & Manuel Díaz-Madroñero, 2020. "Who Risks and Wins?—Simulated Cost Variance in Sustainable Construction Projects," Sustainability, MDPI, vol. 12(8), pages 1-31, April.

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