The article "Cost Underestimation in Public Works Projects: Error or Lie?" by Bent Flyvbjerg, Mette Skamris Holm, and Søren Buhl presents the first statistically significant study on cost escalation in transportation infrastructure projects. The study, based on a sample of 258 projects worth $90 billion, finds that cost estimates used to decide on infrastructure projects are highly and systematically misleading, leading to continuous cost escalation of billions of dollars. The authors examine four explanations for cost underestimation—technical, economic, psychological, and political—and conclude that underestimation cannot be explained by error and is best explained by strategic misrepresentation, i.e., lying. The policy implications suggest that those involved in decision-making should not trust cost estimates and cost-benefit analyses produced by project promoters and their analysts. The study also highlights the need for institutional checks and balances to ensure less deceptive cost estimates.The article "Cost Underestimation in Public Works Projects: Error or Lie?" by Bent Flyvbjerg, Mette Skamris Holm, and Søren Buhl presents the first statistically significant study on cost escalation in transportation infrastructure projects. The study, based on a sample of 258 projects worth $90 billion, finds that cost estimates used to decide on infrastructure projects are highly and systematically misleading, leading to continuous cost escalation of billions of dollars. The authors examine four explanations for cost underestimation—technical, economic, psychological, and political—and conclude that underestimation cannot be explained by error and is best explained by strategic misrepresentation, i.e., lying. The policy implications suggest that those involved in decision-making should not trust cost estimates and cost-benefit analyses produced by project promoters and their analysts. The study also highlights the need for institutional checks and balances to ensure less deceptive cost estimates.