We make an important error in assuming that we can extrapolate what the future will hold based on past events. Equally we err by assuming what the future will hold based on a vivid imagination.

British risk expert John Adams describes an architectural competition in which entrants are supposed to design a building designed to withstand a specifically described terrorist attack (pdf, 3 pages):

Why is this pernicious? It is a classic example of paranoia. The threat that those entering the competition are required to design against is unprecedented. It is a gross exaggeration, a figment of the anticipator‟s imagination.

Meanwhile, Adams goes on to say, more people were killed in road accidents in one week in Britain than died in the July 7, 2005 suicide bomb attacks in London. But we keep imagining and preparing for new catastrophic scenarios at the expense of tangible, correctable accidents and disasters (see: hurricanes, auto accidents).

We can only infer so much about the future from the past, but by building fictionalized scenarios into our plans we overcompensate. It’s generalizing based on fictional evidence.