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A micromort (from micro- and mortality) is a unit of risk defined as one-in-a-million chance of death.[1][2] 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.[3]

Micromorts for future activities can only be rough assessments as specific circumstances will always have an impact. However past historical rates of events can be used to provide a ball park, average figure.

Sample values


Death from Context Time period N deaths N population Micromorts per unit of exposure Reference
All causes England and Wales 2012 499,331 56,567,000 24 per day
8,800 per year
ONS Deaths[4] Table 5.
All causes Canada 2011 242,074 33,476,688 20 per day
7,200 per year
Statistics Canada[5]
All causes US 2010 2,468,435 308,500,000 22 per day
8,000 per year
CDC Deaths[6] Table 18.
Non-natural cause England and Wales 2012 17,462 56,567,000 0.8 per day
300 per year
ONS Deaths[4] Table 5.19.
Non-natural cause US 2010 180,000 308,500,000 1.6 per day
580 per year
CDC Deaths[6] Table 18
Non-natural cause (excluding suicide) England and Wales 2012 12,955 56,567,000 0.6 per day
230 per year
ONS Suicides[7]
Non-natural cause (excluding suicide) US 2010 142,000 308,500,000 1.3 per day
460 per year
CDC Deaths[6] Table 18.
All causes – first day of life England and Wales 2007 430 per first day of life Walker, 2014[8]
All causes – first year of life US 2013 16.7 per day
6100 per year
CDC Life Tables[9]
Blastland & Spiegelhalter, 2014[10]
Murder/homicide England and Wales 2012/13 551 56,567,000 10 per year ONS Crime[11]
Homicide Canada 2011 527 33,476,688 15 per year Statistics Canada[12]
Murder and non-negligent manslaughter US 2012 14,173 292,000,000 48 per year FBI[13] Table 16

Leisure and sport

Death from Context Time period N deaths N exposure Micromorts per unit of exposure Reference
Scuba diving UK: BSAC members 1998–2009 75 14,000,000 dives 5 per dive BSAC[14]
Scuba diving UK: non-BSAC 1998–2009 122 12,000,000 dives 10 per dive BSAC[14]
Scuba diving US – insured members of DAN 2000–2006 187 1,131,367 members 164 per year as member of DAN
5 per dive
DAN[15] p75
Skiing US 2008/9 39 57,000,000 days skiing 0.7 per day Ski-injury.com[16]
Skydiving US 2000–2016 413 48,600,000 jumps 8 per jump USPA[17]
Skydiving UK 1994–2013 41 4,864,268 jumps 8 per jump BPA[18]
Running marathon US 1975–2004 26 3,300,000 runs 7 per run Kipps C 2011[19]
Base-jumping Kjerag Massif, Norway 1995–2005 9 20,850 jumps 430 per jump Soreide 2007[20]
Mountaineering Ascent to Matterhorn 1981–2011 213 about 75,000 ascents

(about 2500 per year)

about 2,840 per ascent attempt Bachmann 2012[21]
Mountaineering Ascent to Mt. Everest 1922–2012 223 5,656 successful ascents 37,932 per ascent NASA 2013[22]


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

  • Travelling 6 miles (9.7 km) by motorbike (accident)[23]
  • Travelling 17 miles (27 km) by walking (accident)[24]
  • Travelling 10 miles (16 km)[25] or 20 miles (32 km)[24] by bicycle (accident)
  • Travelling 230 miles (370 km) by car (accident)[23] (or 250 miles)[24]
  • Travelling 1000 miles (1600 km) by jet (accident)[25]
  • Travelling 6000 miles (9656 km) by train (accident)[23]
  • Travelling 12,000 miles (19,000 km) by jet in the United States (terrorism)[26]


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

Value of a micromort

Willingness to pay

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).[31][32] 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.[32]

Value of a statistical life

Government agencies use a nominal Value of a Statistical Life (VSL) – or Value for Preventing a Fatality (VPF) – to evaluate the cost-effectiveness of expenditure on safeguards. For example, in the UK the VSL stands at £1.6 million for road improvements.[33] Since road improvements have the effect of lowering the risk of large numbers of people by a small amount, the UK Department for Transport essentially prices a reduction of 1 Micromort at £1.60. The US Department of Transportation uses a VSL of US$6.2 million, pricing a Micromort at US$6.20.[34]

Chronic risks

Micromorts are best used to measure the size of acute risks, i.e. immediate deaths. Risks from lifestyle, exposure to air pollution and so on are chronic risks, in that they do not kill straight away, but reduce life expectancy. Ron Howard included such risks in his original 1979 work,[25] for example an additional one micromort from ...

  • Drinking 0.5 liter of wine (cirrhosis of the liver)[25]
  • Smoking 1.4 cigarettes (cancer, heart disease)[25]
  • Spending 1 hour in a coal mine (black lung disease)[25]
  • Spending 3 hours in a coal mine (accident)[25]
  • Living 2 days in New York or Boston in 1979 (air pollution)[25]
  • Living 2 months with a smoker (cancer, heart disease)[25]
  • Drinking Miami water for 1 year (cancer from chloroform)[25]
  • Eating 100 charcoal-broiled steaks (cancer from benzopyrene)[25]
  • Traveling 6000 miles (10,000 km) by jet (cancer due to increased background radiation)[35]

Such risks are better expressed using the related concept of a microlife.

See also


  1. ^ Fry AM, et al. Micromorts—what is the risk?. 2016-02. Accessed 2016-07-30.
  2. ^ Walker KF, et al. The dangers of the day of birth. 2014-05. Accessed 2016-07-30.
  3. ^ Howard, R. A. (1980). J. Richard; C. Schwing; Walter A. Albers (eds.). On making life and death decisions. Societal Risk Assessment: How Safe Is Safe Enough? General Motors Research Laboratories. New York: Plenum Press. ISBN 0306405547.
  4. ^ a b "Deaths Registered in England and Wales (Series DR), 2012" (PDF). Office for National Statistics. 22 October 2013. Retrieved 3 June 2014.
  5. ^ "Leading causes of death, by sex (Both sexes)". Statistics Canada. Retrieved 14 August 2015.
  6. ^ a b c SL Murphy; J Xu & KD Kochanek (8 May 2013). "Deaths: Final Data for 2010" (PDF). US: Centers for Disease Control and Prevention. Retrieved 3 June 2014.
  7. ^ "Suicides in the United Kingdom, 2012 Registrations". Office for National Statistics. 18 February 2014. Retrieved 11 June 2014.
  8. ^ KF Walker; AL Cohen; SH Walker; KM Allen; DL Baines; JG Thornton (13 February 2014). "The dangers of the day of birth". British Journal of Obstetrics & Gynaecology. 121 (6): 714–8. doi:10.1111/1471-0528.12544. PMID 24521517.
  9. ^ "Life Tables". cdc.gov. US: Centers for Disease Control and Prevention. 2013. Retrieved 24 November 2013.
  10. ^ Blastland, Michael; Spiegelhalter, David (2014). The Norm Chronicles: Stories and Numbers About Danger and Death (1 ed.). Basic Books. p. 14. ISBN 9780465085705.
  11. ^ Office for National Statistics (13 February 2014). "Crime Statistics, Focus on Violent Crime and Sexual Offences, 2012/13 – ONS". Retrieved 12 June 2014.
  12. ^ "Leading causes of death, total population, by age group and sex, Canada". Statistics Canada.
  13. ^ Federal Bureau of Investigation. "Crime in the United States, 2012: Table 16". FBI. Retrieved 12 June 2014.
  14. ^ a b British Sub-Aqua Club. "UK Diving Fatalities Review". Archived from the original on 28 July 2014. Retrieved 12 June 2014.
  15. ^ Divers Alert Network (DAN). "Fatalities_Proceedings.pdf" (PDF). Retrieved 12 June 2014.
  16. ^ Ski-injury.com. "Ski Injury". Archived from the original on 28 May 2014. Retrieved 12 June 2014.
  17. ^ United States Parachute Association. "Skydiving Safety". Retrieved 10 April 2018.
  18. ^ British Parachute Association (2012). "How Safe". Archived from the original on 27 July 2014. Retrieved 12 June 2014.
  19. ^ Kipps, Courtney; Sanjay Sharma; Dan Tunstall Pedoe (1 January 2011). "The incidence of exercise-associated hyponatraemia in the London marathon". British Journal of Sports Medicine. 45 (1): 14–19. doi:10.1136/bjsm.2009.059535. PMID 19622524. Retrieved 12 June 2014.
  20. ^ Soreide, Kjetil; Christian Lycke Ellingsen; Vibeke Knutson (May 2007). "How Dangerous is BASE Jumping? An Analysis of Adverse Events in 20,850 Jumps From the Kjerag Massif, Norway". The Journal of Trauma: Injury, Infection, and Critical Care. 62 (5): 1113–1117. doi:10.1097/01.ta.0000239815.73858.88. ISSN 0022-5282. PMID 17495709.
  21. ^ 2,31 MB "Tod am Matterhorn" Check |url= value . Beobachter (in German).
  22. ^ "The World's Tallest Mountain". Earth Observatory. NASA. 2 January 2014.
  23. ^ 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.
  24. ^ a b c "Understanding Uncertainty". Plus Magazine.
  25. ^ a b c d e f g h i j k * Howard, Ron Risky Decisions (Slide show), Stanford University
  26. ^ "The Odds of Airborne Terror". 27 December 2009. Retrieved 17 November 2013.
  27. ^ 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
  28. ^ Blastland, Michael; Spiegelhalter, David (2014). The Norm Chronicles: Stories and Numbers About Danger and Death (1 ed.). Basic Books. p. 8. ISBN 9780465085705.
  29. ^ a b Spiegelhalter, David; Blastland, Michael (30 May 2013). The Norm Chronicles: Stories and numbers about danger (Main ed.). London: Profile Books. ISBN 9781846686207.
  30. ^ Roberts, David C. (22 May 2020). "Putting the Risk of Covid-19 in Perspective". The New York Times. ISSN 0362-4331. Retrieved 6 July 2020.
  31. ^ 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.
  32. ^ a b Russell, Stuart; Norvig, Peter (2009). Artificial Intelligence (3rd ed.). Prentice Hall. p. 616. ISBN 978-0-13-604259-4.
  33. ^ Department for Transport GMH, United Kingdom, "TAG Unit 3.4: The Safety Objective", Transport Analysis Guidance—WebTAG http://www.dft.gov.uk/webtag/documents/expert/unit3.4.1.php
  34. ^ US Department of Transportation, "Treatment of the Economic Value of a Statistical Life in Departmental Analyses—2011 Interim Adjustment", 2011, http://www.dot.gov/policy/transportation-policy/treatment-economic-value-statistical-life
  35. ^ "Radiation dose issues and risk" (PDF). European Society of Radiology. Archived from the original (PDF) on 19 February 2014. Retrieved 18 November 2013.

Further reading

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