Simon,
I will take the time it needs, but I will try to explain exactly what I want to say in my short sentences.
Explaining correctly statistics is NEVER uniaxial! You can't use only one variable to explain a set of data! Or you're absolutely sure to reach totally erroneous conclusion!
A typical simple example (with fictitious datas) : Let's say that we read this fact : "Finnish population have a consumption of firewood by capita a hundred times higher than ugandese population". Then, will we conclude that finnish people have a clear appetite for firewood that ugandese people don't have, and then conclude something about the essence of being finnish?
Or will we add some another axis to sharpen our analysis? Things like average heat in Finland and Uganda during the year, the use of another source of heating in each country, etc...
This example is simple by purpose. Nobody reading "Finnish population have a consumption of firewood by capita a hundred times higher than ugandese population" will conclude "Then finnish people have an huge appetite for firewood", and everybody will understand "Finland is really more cold than Uganda"
Here it's exactly the same!
PS : one hour to write only that!