Now I know why Arbitron carved out a “13^th month” for its radio ratings: Only during Christmastime could WLTE, with “Jingle Bells” in heavy rotation, knock off ratings champs KQ and K102.

The Dec. 10-Jan. 6 “month” exists so Christmastime stunts can be segregated from the rest of the year. LITE-FM dominated in the broadest listenership category (ages 6 or older), pulling in 8.9 percent of the 2.7-million-person Twin Cities market. KQ was second at 8.2 and KDWB was a nose behind at 8.1. Meanwhile, KOOL108, another Christmas clarion, finished fourth with 7.5, well above the 4s it posted throughout 2009.

KQ’s number, which hasn’t cracked double-digits since June, was the lowest of the year.

So who else got slaughtered by Kris Kringle? Country station K102, which has cruised along in the 8s all year, but only posted a 6.1 in the face of Rudolph’s buzzsaw. To a lesser extent, other hurting stations include KS95 (6.2), WCCO (5.9) and MPR News (4.3). You can see 2009’s ratings arc here.

WLTE is owned by CBS, which also owns WCCO, so at the corporate level, the ratings flux more than evened out. KOOL owner Clear Channel also possesses K102 and KDWB, so you can see the virtue of diversification, at least within commercial radio’s constricted formatting. The other big players, such as Citadel (KQ’s owner), Minnesota Public Radio and Hubbard Broadcasting (KS95, AM1500) just had to take their candy-cane-flavored medicine.

KFAN (3.6) held within its yearly range thanks to a pre-choke Vikings. Meanwhile, male-dominated AM1500 tied with its female-dominated sibling, FM107 at 1.6. The Current, which just celebrated its fifth anniversary, pulled in a 1.3, its fifth straight monthly decline, though with a tree-topping asterisk.

The usual disclaimer: Arbitron restricts reporting on the advertiser-coveted 25-to-54 demographic, so this isn't the number station managers care about most. But it's good for seeing trends.

One final cultural note: Christian station KTIS didn’t get a bump from the commercially holy season. The station, owned by Northwestern College, registered a 3.8 share, which is basically the same number it has posted since August.