1 skull in 50,000.  20 pages this size = 1,000,000

We don't usually think about risk consciously when we do something.  By consciously I mean pause and consider how likely there will be a bad result to something we do.

For instance, do you consider the risk of driving somewhere in a car?   What chance is  there of dying?  In the USA the risk of dying in a car in a 230 mile (370Km) is 1 in 1,000,000.  Think Christchurch to Mosgiel.

A 1 in 1,000,000 chance of dying has been given the name 'micromort'

A micromort is a really useful way of thinking about risk, and was introduced by Ronald A Howard in the early 80s.

The picture on the right contains 50,000 icons of a person .  You can see the full size picture here.

So what does a micromort look like?   We'll represent a micromort with a skull icon .

Going back to the driving to Mosgiel example.  1 micromort is 1 skull icon in 20 pictures like the one on the right.  Here's another representation of a micromort. There's one skull in the top left hand corner, and then another 19 pages of the little human icon.


1,000,000 icons / 50,000  icons per page = 20 pages

Just knowing how risky driving a car is doesn't really help you understand much.  We need to compare that risk with other risks.

So here we go, some other things that have a 1 micromort risk associated with them.

  • Living in a house with a smoker for 2 months
  • Going for a 20 minute walk and being killed in an accident
  • Flying 1600 km in a commercial jet and dying in a crash - think Whangarei to Dunedin
  • Eating a Banana and dying from being poisoned by radioactive Potassium 40
  • A days worth of skiing


As you can see there are some things in that list that you would expect, and accept have a risk associated with them.  I hadn't really every considered the risk of going for a walk for 20 minutes, I certainly wouldn't have thought it carried the same risk as flying from Whangarei to Dunedin.

Those risks are all pretty small.  What else have we got

Around 10 micromorts

  • Scuba diving - 5 micromorts per drive
  • Running a marathon - 7 micromorts per marathon
  • Having a general anaesthetic - being put to sleep for an operation 10 micromorts
  • Riding a motorcycle for 100km - 10 micromorts
  • Drowning while going for a swim - 12 micromorts


Around 100 micromorts

  • Getting out of bed at age 75 - 106 micromorts
  • Giving birth - 170 micromorts


Even more dangerous

  • Being born (first day of life) - 430 micromorts
  • BASE jumping - 430 micromorts
  • Getting out of bed at age 90 - 463 micromorts


So now we can start to compare different activities.  Running a marathon is 7 times as risky as going for a 20 minute walk.  Scuba diving is only half as risky as having an operation where you have a general anaesthetic.   Being born may be the riskiest thing you ever do in your life at 430 micromorts.

Professor David Nutt used the idea of a micromort to illustrate relative risk of drug use - a move that was very risky for his career.   Prof Nutt compared taking Ecstasy (MDMA) and horse riding and concluded that they were very similar - about half a micromort each.


At the moment there is only really one thing people are worried about when it comes to risk Covid 19.  So how many micromorts does having a Covid 19 infection carry?   Using global data the mortality rate of Covid 19 is just north of 2%.  So 2 out of every hundred people infected die from Covid-19.  So what's that in micromorts.

1% is equvialent to 10,000 micromorts 2% = 20,000

Here's the maths :  1,000,000 *.01 = 10,000

From that maths the risk of dying from a covid infection is 

20,000 micromorts

So you would have to ride a motorcycle for 100,000 Km to have the same risk of dying as you would from a Covid-19 infection.

Here's the maths : 

  • 10 micromorts per 100km on a motorcycle. 
  • 10,000/10 = 1,000 so Covid is 1000 times riskier than riding a motor
  • 100km x 1,000 = 100,000km  for comparison 100,000km is roughly 2.5 times around the earth at the equator - sorry flat earthers, can't find any numbers for circumference of earth disk.


Vaccine risk is the next thing on people's mind.  There has been a great deal made of vaccine side effects.  And yes all vaccines do have side effects, including Covid-19 vaccines.  The important thing is that they are much less risky than getting Covid-19 itself.  There has been much made in the news of a rare, but not new, side effect of the AstraZeneca vaccine  vaccine-induced prothrombotic immune thrombocytopenia (VIPIT).  It's being openly and vigorously debated in the biological scienctists, so nobody is denying it exists.   There have only been 15 reported deaths out of 17 million people being vaccinated in the UK and Europe.  That's about  0.000088%

Here's the maths:

15 events /17,000,000 vaccinations given

*100 = 0.000088%  (or if you prefer 1 case per 1,133,333 people vaccinated, or roughly 4 cases in the population of NZ)

Back to the micromorts

So if 1% equals 10,000 micromorts

Then the risk of dying from VIPIT is  1/1.133


0.8 micromorts


Remember the risk of dying from a covid infection from before.  I'll remind you


20,000 micromorts


As you can see the risks are hugely different. 


You are 25,000 times more likely to dying from a Covid infection  than you are from VIPIT.   


Or another way 


Being born is

537 times as risky

as getting a COVID vaccination


Get your Covid vaccination when you are offered it.



1 skull in 50,000.  20 pages this size = 1,000,000