From The Art and Popular Culture Encyclopedia
Hindsight bias is the inclination to see events that have occurred as more predictable than they in fact were before they took place. Hindsight bias has been demonstrated experimentally in a variety of settings, including politics, games and medicine. In psychological experiments of hindsight bias, subjects also tend to remember their predictions of future events as having been stronger than they actually were, in those cases where those predictions turn out correct.
One explanation of the bias is the availability heuristic: the event that did occur is more salient in one's mind than the possible outcomes that did not.
It has been shown that examining possible alternatives may reduce the effects of this bias.