I found that different manufacturers often have a different "default foot" profile. For example, Nike is consistently narrow. So that 40% number might be larger

I found that different manufacturers often have a different "default foot" profile. For example, Nike is consistently narrow. So that 40% number might be larger when you consider that people probably shop between brands for comfort as well. There are also some big brands that offer shoes in wide - e.g. New Balance & Cole Hann.