Wednesday, September 24, 2014

Odds of dying in shark attack vs driving to ocean

I've long held that there is a greater chance of dying in a car accident on the way to the ocean than there is of dying from a shark attack in the ocean.  I felt justified in this belief because I know car accidents are a large cause of deaths and that shark attacks are quite rare.  That being said, I never had any numbers to back this up.

The odds of a shark attack vary greatly depending on where you go swimming.  I had the idea briefly of making a map of the US that showed how far you'd have to drive from to equal the odds of dying from a shark attack there.  The problem was in estimating the number of swimmers in each state.

In fact, the only number for annual number of swimmers in the US was this Huffington Post article that claims it is 75 million.  This number seems high, and is unsourced.  The majority of people live near the coast, so it is possible that a quarter of them visit the ocean every year.

Number of shark attacks is easier to estimate.  Wikipedia lists 11 fatal attacks in the US in the 2000s, and 12 in the 1990sThis site lists 1.8 fatal attacks on average per year, and 41.2 injuries per year.

The NHTSA gives us the number for deaths per 100 million miles traveled as 1.13 in 2012.  I assume this includes miles traveled as a passenger. 

Using the 75 million swimmers figure, and the 1.8 fatal attacks and 41.2 injuries figures gives us these results:

You would have to drive 49 miles to have a greater chance of dying in a car accident than being injured by a shark attack.  You would have to drive 2.1 miles to have a greater chance of dying in a car accident than being killed by a shark.

There are a lot of caveats on these numbers.  First, I couldn't find injuries per mile driven, so keep in mind that 49 mile figure is dying in a car accident vs any shark attack injury, and it is also the round trip figure.

As I used the high 75 million swimmer figure, the shark attack odds could be higher.  That is 25% of the US population swimming in the ocean every year.  I would be surprised if the actual figure were lower than 10%, so that only increases the odds by 2.5, which means the round trip distance for equal odds of dying in a car accident vs shark attack would still only be about 5 or 6 miles.

Also, the vast majority of attacks in the US happen in Florida and Hawaii.  Avoid swimming in those two states and you reduce your shark attack odds to at least 1/4. 

No comments:

Post a Comment