Beer is sold via US Customary, but wine and liquor are taxed and sold based on the metric system.
Taxes on distilled spirits have been SI based for a very long time, and there are two primary concerns of the TTB (the regulating body).
Taxes
Consumer protection (label laws)
The primary driver for keeping beer in ounces is to prevent consumer confusion. But the metric measurements on wine and spirits is the official measure.
Here is a link that will show some of their concerns, related to the use of centaliters being prohibited to avoid confusion.
https://www.ttb.gov/pdf/notices_alcohol/notice876.pdf
Taxation is calculated by alcohol by volume, but proof is used because of not just historical reasons but because consumers are use to it. But proof is added as a consumer tool, and not the official standard.
As an example here is the TTB’s requirement for a product to be labeled whisky, note how ‘proof’ is in ().
I can make out, I think, that that Federal statute dates from 1986. If that is true, it is definitely pertinent to “inertia,” the preceding regional history, etc.
To clarify, use of proof is allowed but not required, and if it is used it must be right next to the ABV on products sold in the US and ABV is required.
That was just an example (related to the rise of mini-bottles).
I don’t have access to a historical law library, but I think it was.
T.D. ATF–198, 50 FR 8535, Mar. 1, 1985
IIRC there was a voluntary 10 year window from rules in the 1970’s, right around the same time Canada moved away from the UK units and this date aligns with that.
Then I guess I don’t understand your response to running coach. You were curious whether anybody still labels it by proof. Yes, the US quite often does, even if your experience in Canada is different.
It looks to me (though this is not stated in the Wikipedia article on alcohol proof) as if the original meaning and use of “proof” was as a relatively simple and easily reproducible “field test” for alcohol content - just wet some gunpowder with a sample of the liquor, and try to light the resulting mixture. The lowest alcohol content where the gunpowder would still burn happens to be 57.15%, but that number didn’t matter at the time - they said “let’s call this 100°, and plain water will be zero”. It follows the sensible tradition of choosing an observable reproducible phenomenon as a nice round number on an arbitrary scale.
When, much later, the Americans decided to set a national standard, the “proof” system was obviously well known, and they wouldn’t have wanted to upset the public by eliminating it entirely - but at the same time, the proof scale was arbitrary, and British. So, with greater ability than two hundred years earlier to measure alcohol percentage more directly (i.e. without gunpowder), the Americans decided to set 100 proof at 50% alcohol instead of 57.15%.
And then, later still, some sane person said “We’re measuring the alcohol percentage anyway, and everyone can understand that as it is, so why continue this proof nonsense?”
In my neck of the woods where most everything is metric, 750 ml are often (50% of the time or so) called two-sixes (26 oz) 1.15 l are forties and the 375s are called mickeys. Can’t say I have heard or seen a 250 ml of spirits but I may have simply passed them by on my way to grab a 40 of Bombay.
Correct me if I’m wrong here: when Brits say “let me buy you a pint,” that measurement, even given the obviously loose standards of filling a glass by eye, is that still rationally expected to equal more or less a pint in volume?
FWIW, older Brit cookbooks routinely use “wine-glass” and “demitasse cup” as liquid volume measurements.
And just the other day I read and now can’t remember some strange word Brits use or have used for “half a pint of beer”–what in America is simply called “a short beer.” Anyone know/use it?
“Forty” is a very common term used to refer to 40 oz. bottles of malt liquor (Malt liquor - Wikipedia) - I’ve never come across spirits sold in that size.
The origin is Irish, and they spell it the correct way, whiskey
True, Imperial pints and quarts and gallons are bigger, while metric uses base-10. But US uses base-2, and Imperial uses base-WTF???, so when Skynet takes over the US system will reign supreme!
So, with greater ability than two hundred years earlier to measure alcohol percentage more directly (i.e. without gunpowder), the Americans decided to set 100 proof at 50% alcohol instead of 57.15%.