But unless 100% of Americans use both these services, that is irrelevant, so essentially all you are doing is finding the lowest common denominator - and if you

But unless 100% of Americans use both these services, that is irrelevant, so essentially all you are doing is finding the lowest common denominator - and if you're wanting to do that, why wouldn't you go with defining facebook as "90x more", i.e. 90 / 1 rather than 180 / 2.