NEW YORK (Billboard) – In what is traditionally a high-volume download week thanks to shiny new MP3 players under the tree and download cards stuffed in stockings, a digital sales mark has fallen by the wayside.

Rookie pop singer Ke$ha's "TiK ToK" shifted 610,000 digital tracks for the week ending December 27, according to Nielsen SoundScan. That's the highest weekly sum by a female artist since tracking began in 2003, and the second-best overall after Flo Rida's "Right Round" sold 636,000...