1. This Week in Billboard Chart History: Ke$ha Kicked Off the 2010s at No. 1

    December 29, 2014 8:05 AM EST Her debut smash 'TiK ToK' clocked in as the first new leader of the decade. Plus, remembering key chart feats for the Beatles, the Monkees and Beyonce. Your weekly recap celebrating significant milestones from more than seven decades of Billboard chart history Dec. 29, 2007…