Availability Heuristic

Which kills more people: plane crashes or car accidents? Shark attacks or vending machine accidents? Most people overestimate plane crashes and shark attacks — not because the statistics are hard to find, but because the vivid examples are easy to recall. We judge frequency by availability: if instances come readily to mind, we assume the category is common.

Kahneman and Tversky identified this as the availability heuristic. It’s often useful — things we encounter more frequently really are easier to remember. But availability correlates with more than frequency. Recent, emotional, dramatic, personal events are also more available. The heuristic misfires when these factors diverge from actual probability.

Media amplifies availability errors. News covers plane crashes, not car crashes. Shark attacks make headlines; bee stings don’t. We end up with mental databases that systematically overrepresent dramatic, rare events and underrepresent mundane, common ones. Our intuitive sense of risk is trained on unrepresentative samples.

The heuristic also shapes individual judgment. The doctor who recently saw a rare disease diagnoses it more often. The investor who just witnessed a crash becomes risk-averse. Each vivid example recalibrates our sense of probability — often too far, because the example’s availability outweighs its actual frequency.

Awareness helps but doesn’t cure. Knowing about availability bias doesn’t make vivid examples less available. What helps is actively seeking base rates: looking up actual statistics rather than trusting intuitive frequency estimates. It helps to ask: “Am I judging probability by examples I can recall, or by actual data?”

The practical implication extends beyond risk assessment. Availability shapes what problems seem important, what solutions seem viable, what threats seem real. If an idea is top of mind, it seems more relevant and more likely. Managing availability — yours and others’ — is managing perceived reality.