La predicción de la demanda en evaluación de proyectos

Demand forecasting is a key factor in project evaluation. However, according to recent empirical evidence, long-term predictions are subject to high levels of uncertainty. This paper discusses some relevant topics related to long run demand forecasting with special emphasis on uncertainty. Firstly, we offer a review of the main issues that demand forecasting should consider in order to avoid errors that might distort the result of the evaluation. Secondly, we analyze the pros and cons of alternative modelling approaches, particularly, long term forecast and modal split models. The paper goes on to describe the characteristics of the forecasting errors and provides, as an illustrative example, the impact of uncertainty on long term forecasting for a tolled motorway. Finally, we summarize the forecasting models used in Spain .