It's now 6 months that I run 150km per month. And it's been interesting to track the change it has on my physical health. One of the obscure numbers people track is V02 max, which in short shows how healthy your heart is. But most apps just give you a number, and you think: okay, but what does that mean? Is it good or not?

One app called Health Mate by Withings does something smart: it compares your numbers to other people. For example, it shows me that my score is 54, and the one of a professional basket player one year older than me is 60. And I'm doing better than 95% of the men of the same age. Okay, now I understand that running every day is useful.

This idea is a rule that I also read about in the book Factfulness where the author basically says that when people give you a number you should always ask: "compared to what?". 

Other examples of good comparisons but in the business world are:

Someone telling you your emails are open by 50% of people doesn't mean anything. But when you compare it to the average in your industry, then you know if it's any good. Or someone telling you this department has an overhead of 40 people doesn't mean anything until you compare that number to other departments.