Micromort

This article is about the measure of mortality risk. For the computer program, see Micromort (software).

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.

Sample values

Baseline

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.
	Canada	2011	242,074	33,476,688	20 per day 7,200 per year	Statistics Canada[5]
	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.
	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]
	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]
	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]
	UK: non-BSAC	1998–2009	122	12,000,000 dives	10 per dive	BSAC[14]
	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
Paragliding	Turkey	2004–2011	18	242,355 flights	74 per launch	Canbek 2015[16]
Skiing	US	2008/9	39	57,000,000 days skiing	0.7 per day	Ski-injury.com[17][unreliable source]
Skydiving	US	2000–2016	413	48,600,000 jumps	8 per jump	USPA[18]
	UK	1994–2013	41	4,864,268 jumps	8 per jump	BPA[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]
	Ascent to Mt. Everest	1922–2012	223	5,656 successful ascents	37,932 per successful ascent	NASA 2013[22]

Travel

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

• Travelling 6 miles (9.7 km) by motorcycle (collision)^[23]
• Travelling 17 miles (27 km) by walking (collision)^[23]
• Travelling 10 miles (16 km)^[24] or 20 miles (32 km)^[23] by bicycle (collision)^[a]
• Travelling 230 miles (370 km) by car (collision) (or 250 miles)^[23]
• Travelling 1,000 miles (1,600 km) by jet airplane (collision)^[24]
• Travelling 6,000 miles (10,000 km) by train (collision)^[26]

Other

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

• Hang gliding – 8 micromorts per flight^[23]
• Ecstasy (MDMA) – 0.5 micromorts per tablet, rising to 13 if using other drugs^[27][28]
• Giving birth (vaginal) – 120 micromorts^[29]
• Giving birth (caesarean) – 170 micromorts^[29]
• AstraZeneca vaccination against COVID-19 – 2.9 micromorts^[30]
• COVID-19 infection at age 10 – 20 micromorts
• COVID-19 infection at age 25 – 100 micromorts
• COVID-19 infection at age 55 – 4,000 micromorts
• COVID-19 infection at age 65 – 14,000 micromorts
• COVID-19 infection at age 75 – 46,000 micromorts
• COVID-19 infection at age 85 – 150,000 micromorts (As of December 2020^[update])^[31]

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).^[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 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.^[33]

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 2023^[34]).^[35] 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.^[36]

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]
• Smoking 1.4 cigarettes (cancer, heart disease)^[24]
• Spending 1 hour in a coal mine (black lung disease)^[24]
• Spending 3 hours in a coal mine (accident)^[24]
• Living 2 days in New York or Boston in 1979 (air pollution)^[24]
• Living 2 months with a smoker (cancer, heart disease)^[24]
• Drinking Miami water for 1 year (cancer from chloroform)^[24]
• Eating 100 charcoal-broiled steaks (cancer from benzopyrene)^[24]
• Traveling 6000 miles (10,000 km) by jet (cancer due to increased background radiation)^[37]

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

See also

• Decision analysis – Discipline covering formal decision making
• Decision theory – Branch of applied probability theory
• Ellsberg paradox – Paradox in decision theory
• List of unusual units of measurement
• Microlife – Unit of risk – half an hour of life expectancy
• Pascal's Wager – Argument for the belief in GodPages displaying short descriptions of redirect targets
• Precautionary principle – Risk management strategy
• Risk of ruin – Concept in gambling, insurance, and finance

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]