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.

Huh?

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.