You often hear the argument that motorists are cyclists too. The quantification and truth of that argument depends on what kind of cycling you are referring to.
As the argument is often used to defuse conflicts between motoring and cycling folks (and then quickly starts pointing towards the failed "let's simply share" tactics - a motoring argument btw) I'd suppose regular on-road cycling experience is what we ought to talk about.
I reported previously about the AA study 'Cycling Motorists' and here is the accompanying graphics (see upper right).
To describe it. It's one in five motorists who sport this regular on-road cycling experience so vital to compassion and sympathy towards that cyclist "holding you up" or "not paying road tax" or whatever other myths you can come up with *insert here*.
The figure of non-cycling motorists is in fact is 80%.
So, next time when someone says "motorists are cyclists too" - stop and think. Motorists are very much more likely to NOT do this regular on-road commuter-style cycling (the type of cycling where the conflict, aggression, anger and hurt happens).