Research by St Anne’s Senior Research Fellow, Prof. Bent Flyvbjerg, identifies top 10 biases that could ruin a Christmas holiday or a billion-pound mega-project

From delivering multi-billion-pound infrastructure projects, to planning a family holiday, the world’s leading project management scholar has identified the personal biases to avoid if you want to stay on time and on budget.

Whether it’s an unshakable belief you have all the answers (you don’t), ignoring the odds (at your peril) or throwing money at the problem (you’ll waste it), Bent Flyvbjerg, Oxford Saïd BT Professor and Chair in Major Programme Management Emeritus, has uncovered ten key assumptions and beliefs that can affect decision-making and undermine successful delivery.

Flyvbjerg has also identified ten mega projects severely tripped-up by behavioural bias, including the Channel Tunnel in the UK, Deep Water Horizon in the USA, and the Fukushima Nuclear Power Plant in Japan.

Flyvbjerg said:

‘People who don’t understand bias are like gamblers going to the casino without knowing the odds. They are unlikely to win. Behavioural biases are important because they trip us up, experts and laypeople alike. We need to know what they are, whether we’re planning a new multi-billion-pound high-speed rail line or our next family holiday.’

The paper recognises that behavioural science has seen an explosion in the number of biases identified to over 200. Professor Flyvbjerg identifies the ten most important ones for project management. He stresses the need for leaders in business and government to understand biases, to succeed with their projects.

Flyvbjerg distinguishes between power bias (rooted in politics, including office politics) and cognitive bias (rooted in psychology). He documents how both are overlooked and how this undermines the quality of decisions, with examples from architecture, high-speed rail, movie making, and book publishing.

By adding power bias to behavioural economics, Professor Flyvbjerg develops a more complete version of behavioural science, which has not been done before. Flyvbjerg also shows how bias is best eliminated, for better decisions.

His paper, ‘Top Ten Behavioural Biases in Project Management: An Overview’, is published in Project Management Journal on 14 December 2021.


Flyvbjerg‘s Top 10 behavioural biases in project management: 

  1. Strategic misrepresentation: deliberate misstatement of information.
  2. Optimism bias: overestimation of positives, underestimation of negatives.
  3. Uniqueness bias: seeing plans as more singular than they actually are.
  4. The planning fallacy: underestimation of the time things take.
  5. Overconfidence bias: excessive confidence in own answers to questions.
  6. Hindsight bias: illusion of “I knew it all along.”
  7. Availability bias: overestimation of likelihood of events easily remembered.
  8. The base rate fallacy: ignoring generic odds, focusing on specific cases.
  9. Anchoring: relying on information, just because it’s there.
  10. Escalation of commitment: throwing good money after bad.


Flyvbjerg’s Top 10 projects tripped-up by behavioural bias:

  1. California High-Speed Rail, USA.
  2. Berlin Brandenburg airport, Germany.
  3. Virgil 2-3 Reactors, V.C. Summer Nuclear Power Plant, USA.
  4. Airbus A380, Europe.
  5. Deepwater Horizon, USA.
  6. Fukushima Nuclear Power Plant, Japan.
  7. South China Mall, China.
  8. National Health Service IT System (NPfIT), UK.
  9. Kmart Enterprise Resource Planning IT System, USA.
  10. Channel Tunnel, UK and France.