Not very long ago the Netherlands Court of Audit concluded in its `Schiphol Growth Figures' report that in determining the 1995 PKB for Schiphol's fifth runway, Dutch politicians had based their predictions on projections that were far too optimistic as far as accounting for future air traffic expansion was concerned. The Court of Audit wrote of the situation: `The forecast for the future is, we could have rain or sunshine. It was decided that it would be sunny and so the government ignored the drops that were already falling and went out without umbrellas'. It was only a rain hat that many European air travellers might well opt for high speed train travel. The Court of Audit therefore concluded that where with prediction relating to these kinds of subsidies were concerned, many sorts of presumptions had been put together. Moreover, opposing basic assumptions existed which meant that there was also a degree of internal inconsistency. In this article the conclusions drawn are elucidated by one of the researchers. (A)
Samenvatting