If you only have a few per year then your impaired when you do have them because your body is not adjusted to the affects. Your body builds up a tolerance to the affects so that the more often you drink the less it affects you, the less often you drink the more it affects you. The blood alcohol test is a very poorly implemented standard since the amount of alcohol that affects each person will vary.
Yeah - but when I have my "few per year" - you have to take into account 2 things. 1) I weigh a LOT more than most folks 2)I tend to have my one drink, go up stairs, and go to bed, so any impairment doesn't really matter. 3) If I do have to drive, I wait at least 1 hour after my drink
An example - I went to a Christmas party on the 22nd - had about 2 oz of wine (yes, just a splash) and about 6:00pm - handed the keys to my wife, and said - I don't drive till at least 8:00pm
After that I drank water, apple cider, and gasp - diet coke