We’ve all seen it. That news headline that reads something like:
‘Drinking Unicorn Tears Triples Your Risk of Thumb Cancer’*
“HOLY CRAP!!” you think. “I am NEVER drinking unicorn tears again! I probably have thumb cancer RIGHT NOW!”
These headlines sound scary because they don’t talk about base rates. And that can make all the difference when we are talking about risk. So what is a base rate? It’s simple.
The base rate is how many people are at risk for a thing to begin with. So let’s say that, in general, your risk of getting thumb cancer is 1 in 1o,000 – meaning about 0.01% of people will get thumb cancer.
Risk of thumb cancer = 1/10,000
Pretty low chance, right? But wait – drinking unicorn tears doubles that risk. So let’s say you are an avid unicorn tear drinker. Your risk of getting thumb cancer is now twice what it was.
Risk of thumb cancer if you drink unicorn tears = 1/10,000 x 2 = 2/10,000
Your risk is now 2/10,000 – or 0.02%. So even though doubling sounds like it’s increasing your risk a lot, the rate for thumb cancer among unicorn tear drinkers is still reeeeaaaalllly low.
So what does this all mean? Should you brazenly drink unicorn tears with no regard to thumb cancer at all (this metaphor is starting to weird me out)? Should we ignore increased risk altogether? Of course not. What it means is that before we get in a tizzy, we need to take a deep breath and dig a little further. Find out what the base rate is and what that increased risk actually means. And then make choices based on facts – not fear.
*Note: I do not know what the risk of thumb cancer is. This is just an example. For that matter I don’t know anything about the health effects of unicorn tears either.