Micromort

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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]

Contents

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.

Sample values

Baseline

Death fromContextTime periodN deathsN populationMicromorts per unit of exposureReference
All causesEngland and Wales2012499,33156,567,00024 per day
8,800 per year
ONS Deaths [4] Table 5.
All causesCanada2011242,07433,476,68820 per day
7,200 per year
Statistics Canada [5]
All causesUS20102,468,435308,500,00022 per day
8,000 per year
CDC Deaths [6] Table 18.
Non-natural causeEngland and Wales201217,46256,567,0000.8 per day
300 per year
ONS Deaths [4] Table 5.19.
Non-natural causeUS2010180,000308,500,0001.6 per day
580 per year
CDC Deaths [6] Table 18
Non-natural cause (excluding suicide)England and Wales201212,95556,567,0000.6 per day
230 per year
ONS Suicides [7]
Non-natural cause (excluding suicide)US2010142,000308,500,0001.3 per day
460 per year
CDC Deaths [6] Table 18.
All causes – first day of lifeEngland and Wales2007430 per first day of lifeWalker, 2014 [8]
All causes – first year of lifeUS201316.7 per day
6100 per year
CDC Life Tables [9]
Blastland & Spiegelhalter, 2014 [10]
Murder/homicideEngland and Wales2012/1355156,567,00010 per yearONS Crime [11]
Homicide Canada201152733,476,68815 per yearStatistics Canada [12]
Murder and non-negligent manslaughter US201214,173292,000,00048 per yearFBI [13] Table 16

Leisure and sport

Death fromContextTime periodN deathsN exposureMicromorts per unit of exposureReference
Scuba diving UK: BSAC members1998–20097514,000,000 dives5 per diveBSAC [14]
Scuba divingUK: non-BSAC1998–200912212,000,000 dives10 per diveBSAC [14]
Scuba divingUS – insured members of DAN2000–20061871,131,367 members164 per year as member of DAN
5 per dive
DAN [15] p75
Paragliding Turkey2004–201118242,355 flights74 per launchCanbek 2015 [16]
Skiing US2008/93957,000,000 days skiing0.7 per daySki-injury.com [17] [ unreliable source ]
Skydiving US2000–201641348,600,000 jumps8 per jumpUSPA [18]
SkydivingUK1994–2013414,864,268 jumps8 per jumpBPA [19]
BASE jumping Kjerag Massif, Norway1995–2005920,850 jumps430 per jumpSoreide 2007 [20]
Mountaineering Ascent to Matterhorn1981–2011213about 75,000 ascents

(about 2500 per year)

about 2,840 per ascent attemptBachmann 2012 [21]
MountaineeringAscent to Mt. Everest1922–20122235,656 successful ascents37,932 per successful ascentNASA 2013 [22]

Travel

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

Other

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, 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 is £1 million  GBP in 1997 value (equivalent to £2 million in 2021 [33] ). [34] 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. [35]

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:

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

See also

Notes

  1. however due to the health effects of cycling the net effect of cycling on life expectancy is likely positive in most cases [25]

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Further reading