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A bunch of folks are suing Anheuser-Busch InBev (BUD), claiming the alcohol content of beer brands including Budweiser and Bud Light are watered down from what the company puts on the label. Just one quick question for the plaintiffs: How could you tell?

According to Bloomberg, suits have been filed in Philadelphia, San Francisco, New Jersey, Ohio and Colorado alleging that A-B InBev regularly adds extra water to its finished beers to knock down their alcohol volume below stated amounts. Philadelphia suit filers Thomas and Gerald Greenberg are claiming intimate knowledge of the product, based on their purchase of four cases of Budweiser or more each week for four years. Drinker Brian Wilson, who is suing in federal court in New Jersey, cops to buying a case of Michelob Ultra per month. 

The Greenbergs allege that A-B InBev began using alcohol-measuring instruments known as Anton Paar meters that can measure the alcohol content (known as ABV) in malt beverages to within hundredths of one percent and that it uses those meters to shave the alcohol content. An attorney in California says adding water cuts the stated ABV by 3% to 8%.

Even if both claims are true, however, the already low alcohol content of AB's products may dilute the plaintiffs' case a bit.

The difference between the case against AB and the recent uproar over reduced alcohol content in Maker's Mark is that Beam (BEAM) made it clear it was reducing its bourbon's potency. AB made no such announcement. But the problem is that a 3% to 8% deviation in a 5% ABV beer like Budweiser or 4.2% ABV Michelob Ultra may still fall within the legal margin of error set by the Treasury Department's Alcohol and Tobacco Tax and Trade Bureau

While Twitter users responded to the news with quips feigning surprise and equating Budweiser to Poland Spring, commenters on beer ratings and review site BeerAdvocate were pulling laws and doing the math. Subpart H, section § 7.71, paragraph c of the federal law applying to the labeling and advertising of malt beverages reads as follows:

Tolerances. (1) For malt beverages containing 0.5 percent or more alcohol by volume, a tolerance of 0.3 percent will be permitted, either above or below the stated percentage of alcohol. Any malt beverage which is labeled as containing 0.5 percent or more alcohol by volume may not contain less than 0.5 percent alcohol by volume, regardless of any tolerance.

Under that rule, 5% ABV Budweiser can have alcohol content as low as 4.7%. Michelob Light could legally drop to a near-beer 3.9% ABV. In the U.K. and in America's craft beer community, beer below 4% ABV is considered "session beer" because it lets drinkers have more than one in a session without becoming severely impaired. It's still a bad idea to drink a couple and try to drive, but you can carry on coherent conversation and not get drowsy.

One would think that would be a plus for AB beers often sold in 30-packs, but the Maker's Mark example suggests that consumers are in no mood to pay for a product that's even a fraction less than what they're used to getting. If AB flirted with beer beneath the government's margin for error, the backlash could be more upsetting than the company's Clydesdale Super Bowl commercial.

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