From Slate.com:

Yet it is California that has become the main flash point in the debate over alcohol. Visit any wine shop and you'll quickly see why: the shelves are groaning with California wines in excess of 14 or even 15 percent alcohol, and the labels may not even be telling the full story. Under U.S. law, wines 14 percent or under can vary as much as 1.5 percent from what is stated on the label (as long as the actual content does not surpass 14 percent), and those above 14 percent are permitted a 1 percent margin of error. Although California has always produced its share of floozies (I'm still talking about wines), Napa cabernets and merlots generally weren't as heady in the past. A recent study led by University of California Davis professor Julian Alston found that sugar levels in California grapes have jumped 9 percent since 1980.

For more, see: Hedonistic Fruit Bombs