I'm after information concerning shower outlet heights in the USA. 
What I would like to know is:
How high up the wall are shower outlets generally installed in the USA?
I'm after the measurement at the wall, not to the actual shower head itself.
A range of measurements is expected.  Depending on the depth of the
information that can be found, it would be very helpful if the data
could possibly be grouped in meaningful ways, such as dwelling type
(eg; apartment, multi-storey house, etc), geographic location, shower
wall material (eg; tiles), dwelling and/or bathroom age, dwelling
occupant profiles (eg; number of adults, children, their sex and
ages), whether the shower head is over a bath or in a shower
enclosure, etc.
The purpose of the answer to this question is to build a better
understanding of the shower environment in the USA for ergonomic
evaluation purposes.  If there are market surveys that can be
purchased with this kind of information, that would also be of great
interest.  Geographically we have a preference for measurements from
the East Coast and Illinois (Chicago).