As to how does Christmas Music help AC stations: If you look at the 12+ numbers across most markets, the station that goes wall to wall Christmas first, (unless a challenger does it a day or two before the formatic leader, then the leader wins anyway) usually enjoys it's best book of the year. I don't get it, perhaps like many here, being too Radiocentric in my thought patterns but it gets the stations played in retail spots not usually on and sampling goes way up. The biggest day is 12/26 when they tune back in...some stay some don't. It's also becoming a way to back out of a format with as little hassle as possible.
It's such a numbers distorting phenomenom that Arbitron is planning, with the implementation of the people meter, 13 four week surveys, 12 months and the 13th...Holiday.Then all the Christmas distortion will be where it should be and falsely impact one 13th of the ratings rather than one fourth, as the Fall book currently does. More accuracy..a good thing and less xmas hype.