Sottostima dei costi dei progetti di opere repubblich: errore casuale o intenzionale?

This article presents results from the first statistically significant study of cost escalation in transportation infrastructure projects. Based on a sample of 258 transportation infrastructure projects worth $90 billion (U.S.), it is found with overwhelming statistical significance that the cost estimates used to decide whether important infrastructure should be built are highly and systematically misleading. The result is continuous cost escalation of billions of dollars. The sample used in the study is the largest of its kind, allowing for the first time statistically valid conclusions regarding questions of cost underestimation and escalation for different project types, different geographical regions, and different historical periods. Four kinds of explanation of cost underestimation are examined: technical, economic, psychological, and political. Underestimation cannot be explained by error and is best explained by strategic misrepresentation, i.e., lying. The policy implications are clear: In debates and decision making on whether important transportation infrastructure should be built, those legislators, administrators, investors, media representatives, and members of the public who value honest numbers should not trust the cost estimates and cost-benefit analyses produced by project promoters and their analysts. Independent estimates and analyses are needed as are institutional checks and balances to curb deception.