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A micromort is a unit of risk measuring a one-in-a-million probability of death (from micro- and mortality). Micromorts can be used to measure riskiness of various day-to-day activities. A microprobability is a one-in-a million chance of some event; thus a micromort is the microprobability of death. The micromort concept was introduced by Ronald A. Howard who pioneered the modern practice of decision analysis.[1]

Human values[edit]

Typical value around $50 in 2009[edit]

An application of micromorts is measuring the value that humans place on risk: for example, one can consider the amount of money one would have to pay a person to get him or her to accept a one-in-a-million chance of death (or conversely the amount that someone might be willing to pay to avoid a one-in-a-million chance of death). When put thus, people claim a high number but when inferred from their day-to-day actions (e.g., how much they are willing to pay for safety features on cars) a typical value is around $50 (in 2009).[2][3] However utility functions are often not linear, i.e the more a person has already spent on their safety the less they are willing to spend to further increase their safety. Therefore the $50 valuation should not be taken to mean that a human life (1 million micromorts) is valued at $50,000,000. Furthermore the local linearity of any utility curve means that the micromort is useful for small incremental risks and rewards, not necessarily for large risks.[3]


The average risk of dying per day can be calculated from the average lifetime. Assuming this is 70 years, that means there is one death for every 25,550 days lived (70 × 365 = 25,550).

The number of micromorts per day is one million divided by that number of days; in this case, about 39 micromorts acquired individually every day. The number of micromorts per day is divided by 24 hours; that is about 1.63 micromorts per hour. This is just an average across an entire population: the number of micromorts per day will vary across different categories of people, such as by age, sex and lifestyle.

An alternative way of getting the same figure is to take the number of people dying each day in the UK (about 2500), and divide it by the total population (60 million) which gives 41.6 micromorts.

These figures include all deaths across a population. When natural deaths are excluded, the result measures the risk of premature death, which is roughly one micromort per day. In the UK, approximately 50 people die each day, on average, from non-natural causes .[4]


Activities that increase the death risk by roughly one micromort, and their associated cause of death:

  • Diving 15meters (Bends)[citation needed]
  • Drinking 0.5 liter of wine (cirrhosis of the liver)[5]
  • Smoking 1.4 cigarettes (cancer, heart disease)[5]
  • Spending 1 hour in a coal mine (black lung disease)[5]
  • Spending 3 hours in a coal mine (accident)[5]
  • Living 2 days in New York or Boston in 1979 (air pollution)[5]
  • Living 2 months with a smoker (cancer, heart disease)[5]
  • Drinking Miami water for 1 year (cancer from chloroform)[5]
  • Eating 100 charcoal-broiled steaks (cancer from benzopyrene)[5]
  • Eating 40 tablespoons of peanut butter (liver cancer from aflatoxin B)[5]
  • Eating 1000 bananas (cancer from radioactive 1 kBED of Potassium-40)[citation needed]
  • Travelling 6 minutes by canoe (accident)[5]
  • Travelling 6 miles by motorbike (accident)[6]
  • Travelling 17 miles by walking (accident)[7]
  • Travelling 10 miles[5] (or 20 miles[7]) by bicycle (accident)
  • Travelling 230 miles (370 km) by car (accident)[6] (or 250 miles[7])
  • Travelling 6000 miles (9656 km) by train (accident)[6]
  • Travelling 1000 miles (1600 km) by jet (accident)[5]
  • Travelling 6000 miles (10,000 km) by jet (cancer due to increased background radiation)[8]
  • Travelling 12,000 miles (19,000 km) by jet in the United States (terrorism)[9]

Increase in death risk for other activities on a per event basis:

See also[edit]


  1. ^ Howard, R. A. (1980). J. Richard, C. Schwing, Walter A. Albers, ed. "On making life and death decisions". Societal Risk Assessment: How Safe Is Safe Enough? General Motors Research Laboratories. New York: Plenum Press. ISBN 0306405547. 
  2. ^ Howard, R. A. (1989). "Microrisks for Medical Decision Analysis". International Journal of Technology Assessment in Health Care 5 (3): 357–370. doi:10.1017/S026646230000742X. PMID 10295520. 
  3. ^ a b Russell, Stuart; Norvig, Peter (2009). Artificial Intelligence (3rd ed.). Prentice Hall. p. 616. ISBN 0-13-604259-7. 
  4. ^ ONS Mortality statistics [1], UK Office of National Statistics 2009, ISSN 1757–1375, accessed 2010-12-08
  5. ^ a b c d e f g h i j k l * Howard, Ron Risky Decisions (Slide show), Stanford University
  6. ^ a b c d Spiegelhalter, David (10 February 2009). "230 miles in a car equates to one micromort: The agony and Ecstasy of risk-taking". The Times (London). Retrieved 19 April 2009. 
  7. ^ a b c d "Understanding Uncertainty". Understanding Uncertainty. Retrieved 2013-08-24. 
  8. ^ "Radiation dose issues and risk". European Society of Radiology. Retrieved 2013-11-18. 
  9. ^ "The Odds of Airborne Terror". 2009-12-27. Retrieved 2013-11-17. 
  10. ^ Ange, Michael. "The 2010 DAN Diving Fatalities Workshop". Alert Diver. Retrieved 2013-08-24. 
  11. ^ "Skydiving Safety". Uspa.org. Retrieved 2013-08-24. 
  12. ^ Advisory Council on the Misuse of Drugs. MDMA ('ecstasy'): a review of its harms and classification under the Misuse of Drugs Act 1971. London: UK Home Office, 2009: p 18. http://www.homeoffice.gov.uk/publications/agencies-public-bodies/acmd1/mdma-report

Further reading[edit]