[vlod]

Also in the US (probably due to lack of training and the customer too embarrassed to complaining) tend not to fill it the brim (and so not even 16''). I've seen 2-3 inch heads and asked them to top it up. They look at me as if I've just insulted George Washington.

[mcjiggerlog]

Well, depending on the type of beer, that's intentional. It's not always the faux-pas that it would be to do this when serving cask ale in the UK.

[bardak]

But usually when that is the case they will use glassware that has a 20oz line on the glass with room for the head.