@mellowyellow Understand your concerns for your 'girls'. Hope you can find a way to talk to them about it that still keeps lines of communications open.
As to the numbers given i have a lot of questions. How did they arrive at that figure? People arrested for driving drunk? Self-report (notoriously bad info--more people claim a positive behavior and deny a negative one than actually
do whatever in reality), AA groups? Did they count 'binge' or just daily drinkers? Even if you just get blotto on weekends or once a month or a few times a year, if you can't resist the urge to drink or refrain from some activity that encourages it (clubbing, parties at private homes, throwing a self-pity party by your lonesome) you still have issues with alcohol.
Alcohol indeed is a common, because legal and comparatively cheap compared to the illegal drugs, self-medication. (Tho if you 'gotta have it'--even a high end wine, whiskey, rum, liquor 'addiction' still counts as alcoholism.) But alcohol is more addictive to some than to others, and that probably has to do with differences in their bodies/brains. What is more there have been studies that showed that many people use alcohol as an excuse for behaviors they don't allow themselves when sober. For those it may actually be more psychologically addictive than physical and with motivation and effort they could learn to drink in moderation or refrain entirely.
i've seen most every form alcoholism within my family from my Irish Granny to my kids (Boys got double whammy of any genetic component--between paternal Grandma, my Mom, and their Dad. i 'flirted' with it in my youth, But ultimately decided i was in charge. i can have a beer or a shot on the rare occasions i want one without then having to have a string of them. Both of my sons the same, tho they both had to go thru hangovers (more for one than the other) to decide they needed to control it not vice versa. My daughter, for a variety of reasons including some alcoholics on both sides of her family tried wine coolers when she came of age, and never wanted them or any other alcohol again. She's even careful about OTC pain killers because she's so concerned she might become 'addicted'.