The underestimation of project duration: an explanation in terms of a time-horizon

The thesis of this note is that time is inherently underestimated because estimators are influenced by a time-horizon which has no objective existence. The bias will increase with the complexity, unfamiliarity and uncertainty of the task. Implications of this are indicated, and its bearing on a study recently published in this journal is briefly touched upon. An independent test would probably require the methods of individual or social psychological research. The possibility of improving time-estimation would exist if the time-horizon to which individuals are subject could be ascertained.