A micromort (from

micro- ''Micro'' (Greek letter μ ( U+03BC) or the legacy symbol µ (U+00B5)) is a unit prefix in the metric system denoting a factor of 10−6 (one millionth). Confirmed in 1960, the prefix comes from the Greek ('), meaning "small". The symbol for ...

and mortality) is a unit of

risk In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environm ...

defined as a one-in-a-million chance of

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

. 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 Ronald Arthur Howard (born August 27, 1934) is an emeritus professor in the Department of Engineering-Economic Systems (now the Department of Management Science and Engineering) in the School of Engineering at Stanford University. Howard directs te ...

who pioneered the modern practice of

decision analysis Decision analysis (DA) is the discipline comprising the philosophy, methodology, and professional practice necessary to address important decisions in a formal manner. Decision analysis includes many procedures, methods, and tools for identifyi ...

. 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 A ballpark, or baseball park, is a type of sports venue where baseball is played. The playing field is divided into the infield, an area whose dimensions are rigidly defined, and the outfield, where dimensions can vary widely from place to pla ...

, average figure.

Sample values

Baseline

Leisure and sport

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) * Travelling 17 miles (27 km) by walking (collision) * Travelling 10 miles (16 km) or 20 miles (32 km) by bicycle (collision) * Travelling 230 miles (370 km) by car (collision) (or 250 miles) * Travelling 1,000 miles (1,600 km) by jet (collision) * Travelling 6,000 miles (9,656 km) by train (collision)

Other

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

Hang gliding Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered ...

– 8 micromorts per trip * Ecstasy (MDMA) – 0.5 micromorts per tablet, rising to 13 if using other drugs 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 * Giving birth (

vaginal In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen. ...

) – 120 micromorts * Giving birth (

caesarean Caesarean section, also known as C-section or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen, often performed because vaginal delivery would put the baby or ...

) – 170 micromorts *

AstraZeneca AstraZeneca plc () is a British-Swedish multinational pharmaceutical and biotechnology company with its headquarters at the Cambridge Biomedical Campus in Cambridge, England. It has a portfolio of products for major diseases in areas includi ...

vaccination against

COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was identified in Wuhan, China, in December 2019. The disease quick ...

– 2.9 micromorts *

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 CC-BY icon

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.

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). 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.

Value of a statistical life

Government agencies use a nominal Value of a Statistical Life (VSL) – or

Value for Preventing a Fatality The value of life is an economic value used to quantify the benefit of avoiding a fatality. It is also referred to as the cost of life, value of preventing a fatality (VPF), implied cost of averting a fatality (ICAF), and value of a statistical li ...

(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. Since road improvements have the effect of lowering the risk of large numbers of people by a small amount, the

UK Department for Transport The Department for Transport (DfT) is a department of His Majesty's Government responsible for the English transport network and a limited number of transport matters in Scotland, Wales and Northern Ireland that have not been devolved. The d ...

essentially prices a reduction of 1 micromort at £1.60. The

US Department of Transportation The United States Department of Transportation (USDOT or DOT) is one of the executive departments of the U.S. federal government. It is headed by the secretary of transportation, who reports directly to the President of the United States a ...

uses a VSL of US$6.2 million, pricing a micromort at US$6.20.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

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, for example an additional one micromort from: * Drinking 0.5 liter of wine (cirrhosis of the liver)* Howard, Ro
Risky Decisions
(Slide show), Stanford University * Smoking 1.4 cigarettes (cancer, heart disease) * Spending 1 hour in a coal mine (black lung disease) * Spending 3 hours in a coal mine (accident) * Living 2 days in New York or Boston in 1979 (air pollution) * Living 2 months with a smoker (cancer, heart disease) * Drinking Miami water for 1 year (cancer from chloroform) * Eating 100 charcoal-broiled steaks (cancer from benzopyrene) * Traveling 6000 miles (10,000 km) by jet (cancer due to increased background radiation) Such risks are better expressed using the related concept of a microlife.

Sample values

Baseline

Leisure and sport

Travel

Other

Value of a micromort

Willingness to pay

Value of a statistical life

Chronic risks

See also

Notes

References

Further reading