Alcohol labeling on wine

With all the noise being made about rising alcohol levels on California and other New World wines (and some Old World wines) "buying by alcohol percent" may be happening with some consumers.   I know I've started looking and will sometimes form opinions on a wine before even trying it.   This is something most wineries and retail sales folks would prefer you didn't do.

A 15% alcohol Pinot.
Or is it closer to 16%?

So what can you tell by reading the percent alcohol number on a wine label?   Does it really give you an idea of what kind of wine you're getting?    Well, maybe a little bit.

A wine labeled 14.5% alcohol doesn't necessarily have 14.5%.   There's a fudge factor allowed by the government mostly to cover variances in what actually shows up in the bottle as labels have to be ordered well before bottling.  

But this fudge factor is huge.   A wine labeled 14.5% could actually be 15.4%.  The law is a little convoluted as the rules and taxes are different for wines below and above 14%.   This law is old and from a time when table wines were pretty much always below 14%.  In fact, wines under 14% don't have to state the alcohol content though most do.

So not only does this mean you may really be getting a much higher (or lower) alcohol wine, but if you're comparing two, say one labeled as 14.5% and another at 15% you can't really assume the latter is higher in alcohol.   The numbers are reported by the wineries to the gov't so they're trusting the producers to be accurate.   Is there any cheating going on?  I don't know, but I would guess any gov't checking would be for wines labeled at 14% and just under to see if they really belong in the lower tax bracket because the gov't mostly cares about their money.