Short description: Unit of risk – one-in-a-million chance of death
A micromort (from micro- and mortality) is a unit of risk defined as a one-in-a-million chance of death.[1][2] Micromorts can be used to measure the 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 rough estimate.
COVID-19 infection at age 85 – 150,000 micromorts ((As of December 2020))[30]
Value of a micromort
Willingness to pay
An application of micromorts is measuring the value that humans place on risk. For example, a person can consider the amount of money they would be willing to pay to avoid a one-in-a-million chance of death (or conversely, the amount of money they would receive to accept a one-in-a-million chance of death). When offered this situation, people claim a high number. However, when looking at their day-to-day actions (e.g., how much they are willing to pay for safety features on cars), a typical value for a micromort is around $50 (in 2009).[31][32] This is not to say the $50 valuation should be taken to mean that a human life (1 million micromorts) is valued at $50,000,000. Rather, people are less inclined to spend money after a certain point to increase their safety. This means that analyzing risk using the micromort is more useful when using small risks, not necessarily large ones.[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,[24] for example, an additional one micromort from:
Drinking 0.5 liter of wine (cirrhosis of the liver)[24]
Risk of ruin – Concept in gambling, insurance, and finance
Notes
↑however due to the health effects of cycling the net effect of cycling on life expectancy is likely positive in most cases[25]
References
↑Fry, A.M.; Harrison, A.; Daigneault, M. (February 2016). "Micromorts - what is the risk?". British Journal of Oral and Maxillofacial Surgery54 (2): 230–231. doi:10.1016/j.bjoms.2015.11.023. PMID26747014.
↑Walker, KF; Cohen, AL; Walker, SS; Allen, KM; Baines, DL; Thornton, Jg (May 2014). "The dangers of the day of birth". BJOG121 (6): 714–718. doi:10.1111/1471-0528.12544. PMID24521517.
↑J. Richard, ed (1980). "On making life and death decisions". Societal Risk Assessment: How Safe Is Safe Enough? General Motors Research Laboratories. New York: Plenum Press. ISBN0306405547.
↑KF Walker; AL Cohen; SH Walker; KM Allen; DL Baines; JG Thornton (2014-02-13). "The dangers of the day of birth". British Journal of Obstetrics and Gynaecology121 (6): 714–8. doi:10.1111/1471-0528.12544. PMID24521517.
↑Blastland, Michael; Spiegelhalter, David (2014). The Norm Chronicles: Stories and Numbers About Danger and Death (1 ed.). Basic Books. p. 14. ISBN9780465085705.
↑Soreide, Kjetil; Ellingsen, Christian Lycke; Knutson, Vibeke (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 Care62 (5): 1113–1117. doi:10.1097/01.ta.0000239815.73858.88. PMID17495709.
↑Blastland, Michael; Spiegelhalter, David (2014). The Norm Chronicles: Stories and Numbers About Danger and Death (1 ed.). Basic Books. p. 8. ISBN9780465085705.
↑ 28.028.1Spiegelhalter, David; Blastland, Michael (2013-05-30) (in en). The Norm Chronicles: Stories and numbers about danger (Main ed.). London: Profile Books. ISBN9781846686207.
↑"Microrisks for Medical Decision Analysis". International Journal of Technology Assessment in Health Care5 (3): 357–370. 1989. doi:10.1017/S026646230000742X. PMID10295520.
↑ 32.032.1Russell, Stuart; Norvig, Peter (2009). Artificial Intelligence (3rd ed.). Prentice Hall. p. 616. ISBN978-0-13-604259-4.