Well I found a 15. There’s a UNESCO agency named
IOC Intergovernmental Oceanographic Commission = 13.3…
and the French version of that name is
COI Commission Océanographique Intergouvernementale = 15
OBTW (2.25), IFF (1.33) doesn’t seem to pass the Google test, so OBTW seems to be the shortest so far…
Wow, thats a good link. A quick perusal turns up:
G (Federal Reserve Bank of Chicago, Illinois) - 35 or 33
I’m not sure how to define ‘acronym’ now.
What if, for a working definition we defined an acronym as a series of letters, created by taking the initial letters of a name or a series of words, used in lieu of the original words to represent them.
I’m still chuckling over the South African society to fight lung disease. 
Do languages other than English count? I saw someone use French, and I’m sure some German Dopers can give us some really long ones. I’ll start it at Deutsche Gruppenpsychotherapeutische Gesellschaft (DGG)=15.66…
This is more of a game/puzzle than a GQ, so I’ll move this thread to MPSIMS.
bibliophage
moderator GQ
I did seem to open a potential can of worms with that French example. I was desperate to find a 15 or better. But since it’s open, how about
GAA Gesellschaft für Arzneimittelanwendungsforschung und Arzneimittelepidemiologie = 22.6…
I haven’t tried to translate it, but it’s the name of some medical organization.
Other languages count as long as they come up on Google. Didn’t see DGG or GAA on google, which sort of means they’re a bit too obscure.