Amicromort (frommicro- andmortality) is a unit ofrisk defined as a one-in-a-million chance ofdeath.[1][2] Micromorts can be used to measure the riskiness of various day-to-day activities. Amicroprobability is a one-in-a million chance of some event; thus, a micromort is the microprobability of death. The micromort concept was introduced byRonald A. Howard who pioneered the modern practice ofdecision 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.
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 bewilling to pay to avoid a one-in-a-million chance of death (or conversely, the amount of moneythey 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).[32][33] 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 areless 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.[33]
Government agencies use a nominalValue of a Statistical Life (VSL) – orValue for Preventing a Fatality (VPF) – to evaluate the cost-effectiveness of expenditure on safeguards. For example, in the UK, the VSL is £1 million GBP in 1997 value (equivalent to £2 million in 2023[34]).[35] Since road improvements have the effect of lowering the risk of large numbers of people by a small amount, theUK Department for Transport essentially prices a reduction of 1 micromort at £1.60. TheUS Department of Transportation uses a VSL of US$6.2 million, pricing a micromort at US$6.20.[36]
Micromorts are best used to measure the size ofacute risks, i.e. immediate deaths. Risks from lifestyle, exposure toair pollution, and so on arechronic 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 ofwine (cirrhosis of the liver)[24]
^Fry, A.M.; Harrison, A.; Daigneault, M. (February 2016). "Micromorts - what is the risk?".British Journal of Oral and Maxillofacial Surgery.54 (2):230–231.doi:10.1016/j.bjoms.2015.11.023.PMID26747014.
^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.ISBN0306405547.
^Blastland, Michael; Spiegelhalter, David (2014).The Norm Chronicles: Stories and Numbers About Danger and Death (1 ed.). Basic Books. p. 14.ISBN9780465085705.
^United States Parachute Association."Skydiving Safety".Archived from the original on 22 August 2018. Retrieved10 April 2018.
^British Parachute Association (2012)."How Safe". Archived fromthe original on 27 July 2014. Retrieved12 June 2014.
^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 Care.62 (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.
^abSpiegelhalter, David; Blastland, Michael (30 May 2013).The Norm Chronicles: Stories and numbers about danger (Main ed.). London: Profile Books.ISBN9781846686207.
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