ABSTRACT
Public and private institutions have always had to make decisions about whether or not to invest in projects intended to provide society with new goods and services. Their predominant concerns will be how long a project will take to complete and how much it will cost. Their decisions will depend to a significant extent on the degrees of confidence they have in the accuracy of each of these two parameters, accuracy that project development works hard to increase. I suspect this lack of confidence comes from the persistent tendency for projects to overspend and overrun, and that it is a caution nurtured by experience.
