Do you say 'bye' before you hang up the phone?

bubble_tea
I noticed in American TV shows and movies, people hardly ever do that before they hang up the phone. They just hang up after they said what they had to say and the other party hears the phone click. O_O
Is this an American thing to do or does it only happen on screen?
Updates
+1 y
http://youtu.be/APUQeQalRsU

I found a nice compilation of movie phone hang ups hahahaha xD
Do you say 'bye' before you hang up the phone?
50 Opinion