This was originally a social video.
You might have seen Robert F. Kennedy Jr. make a statistics mistake today.
Rather than clown on it, I wanted to explain the simple and interesting concept behind the gaff.
RFK: “And I said, well, if the drug was $100 and it raised the price to $600, that would be a 600% rise. If it drops from 600 to 100, that’s a 600% savings.”
I’m not one to judge because I’ve made lots of numeracy mistakes in my day, including in my journalism. And statistics actually are complicated, but they’re
cool. So, it’s worth looking at what’s happening here.
The core concept to get is that percent change isn’t about the difference between two numbers. It’s about the difference relative to where you started. Let’s look at apples, shall we? Going from one apple to five apples, you gained four apples compared to one. But going from five apples down to one means you lost four apples compared to
the five you started with.
One compared to four is a big difference. Five compared to four is a smaller difference. It’s the same four apples, but it’s a different starting point. It’s a different percentage.
And of course, the gut check, the real reminder is that you can never lose more than
100% of a physical thing. So, anytime anyone says you had a 600% drop of a physical thing, you know something’s off.
To RFKs example, going from $600 to $100 is $500 divided by $600 (83%). Going $100 to $600 is $500 divided by $100 (500%). You divide by the starting point, hence the difference.
Percentages aren’t reversible. They’re anchored to where you started.