Ron Roizen brought to my attention Philip J. Pauly [1950-2008], "Is
Liquor Intoxicating?  Scientists, Prohibition, and the Normalization
of Drinking," American Journal of Public Health 84 (February 1994).
It answers several of my questions and raises a few more.

Pauly pointed out that the "more than 0.5" used by the Volstead Act
was originally the line at which the federal government and some
states started taxing alcoholic beverages.  I assume that this was 0.5
ABW but the Volstead excerpt that I have seen wasn't clear and some
Internet sources say ABV.  According to Pauly, brewers and their
supporters argued that the Volstead Act should have made "more than
2.75 ABW" the definition of intoxication.  In 1933, when political
power had swung from the teetotalers to the repealers, the brewers and
their supporters asked for and got a still higher alcoholic content as
defining intoxicating, "more than 3.2 ABW."  It remains unclear why
3.2 and not 3.0 or 3.5 or even 4.0 was chosen.

Questions: (!) was "more than 0.5" ABW or ABV? (2) why specifically
"more than 3.2 ABW"? (3) is 3.2 beer ABW almost as strong as the
weakest "light beers" marketed in the USA today?

About 3.2 beer college towns.  When I came to Oxford (Ohio) in 1969,
people in search of a stronger drink than 3.2 either went to adjacent
Indiana for a bottle or half-way to the city of Hamilton for a glass.
College Corner is a town that is partly in Ohio and partly in Indiana.
 Just over the Indiana line is a package store called the Bias, not
because of its prejudices but because it located at an angle just
outside Ohio.  Oxford residents who wanted to drink in a restaurant
drove in the other direction toward Hamilton and stopped at the Shady
Nook.  It had undistinguished food, a full bar, and a theater organ
that when played rose up from behind the bar in a cloud of bubbles.
When Oxford repealed 3.2 the Shady Nook died, and the Bias lost much
of its business.

Having lived in four American states and having visited many others, I
regard their liquor laws as a palimpsest that reminds us of past
ideological battles.

David

-- 
David M. Fahey
Professor Emeritus of History
Miami University
Oxford, Ohio 45056
USA