Hindsight bias

Hindsight bias, also known as the knew-it-all-along phenomenon^[1] or creeping determinism,^[2] is the common tendency for people to perceive past events as having been more predictable than they were.^[3][4]

After an event has occurred, people often believe that they could have predicted or perhaps even known with a high degree of certainty what the outcome of the event would be before it occurred. Hindsight bias may cause distortions of memories of what was known or believed before an event occurred and is a significant source of overconfidence in one’s ability to predict the outcomes of future events.^[5] Examples of hindsight bias can be seen in the writings of historians describing the outcomes of battles, in physicians’ recall of clinical trials, and in criminal or civil trials as people tend to assign responsibility on the basis of the supposed predictability of accidents.^[6][7][2]

In some countries, 20/20 indicates normal visual acuity at 20 feet, from which derives the idiom "hindsight is 20/20".