The U.S. Code of Federal Regulations, Title 27, Chapter 1, part 7, etc., etc., etc. says that “the terms ‘low alcohol’ or ‘reduced alcohol’ may be used only on malt beverages containing less than 2.5 percent alcohol by volume” and that nonalcoholic beer must contain less than 0.5 percent alcohol by volume.
By volume? Yes, by volume. That’s another fairly recent change.
Various brewers had been in the habit of expressing alcohol contents as percent by weight: how many grams of alcohol there are in 100 grams of brew. Others had been accustomed to expressing it as percent by volume: how many milliliters of alcohol there are in 100 milliliters of brew.
But again, the U.S. Code of Federal Regulations, Title 27, etc. has stepped in: “Statement of alcoholic content shall be expressed in percent alcohol by volume, and not by percent by weight.”
That’s good, because the alcoholic contents of wines and distilled beverages are also expressed as percent by volume, so now they’re all consistent.