What is the availability heuristic?

Guessing how likely something is by how easily examples come to mind. Loud, recent things feel more likely than they are.

Plane crashes feel more dangerous than car rides because you've seen every crash and none of the safe landings. News is a machine for making rare things memorable, which quietly breaks your sense of what's normal.

In markets it's tradeable: after one shock upset, the crowd overprices the next one for weeks. When a percent is drifting on a headline's afterglow rather than new evidence, availability is doing the pricing, and fading it is often the sharp side.