Risk basics
Definitions, formats, common thinking errors, and a clear framework for comparing choices.
If a number lacks a denominator (out of what, over what time), it is not a risk.
Risk is not fear
Fear is a feeling. Risk is a measurable idea: a chance that an outcome happens. You can be afraid of something with a tiny risk, and calm about something with a large risk.
Common formats you will see
- 1 in N (example: 1 in 100)
- Percent (example: 1%)
- Rate per time (example: per year)
- Rate per distance (example: per 100,000 km)
A number without a denominator is not a risk. “10 cases” is not helpful unless you know “out of 10,000 people” and the time period.
Why humans misjudge risk
Availability bias
We overestimate events we can easily remember (because they were vivid, recent, or on the news).
Base-rate neglect
We ignore how common something is in the first place (the “base rate”).
Relative vs absolute risk
“Doubles your risk” can still be small if you started very small. Ask for absolute numbers.
Survivorship bias
We see the stories of those who made it, not those who did not.
Risk reduction options
- Avoid: choose a different activity or exposure.
- Reduce likelihood: training, maintenance, screening, safer environments.
- Reduce impact: seat belts, helmets, ICU access, insurance, emergency plans.
- Transfer: insurance, contracts, diversification (some domains).
- Accept: if the remaining risk is small or aligned with your values.
Tip: if you are comparing options, keep the same unit (per year, per trip, per 100,000 people) and the same population (age, health, location).