Katy Perry's new song Roar is set to sell around 450,000 downloads by the end of Billboard's tracking week tomorrow, Sunday August 18th! Lady Gaga's Applause is set to sell between 200,000 and 225,000 downloads. Before Little Monsters kill me we have to see that Katy's single has 1 more day worth of sales than Gaga's. Still this is great news for both singers! Roar is the lead single of Prism, out on October 22nd and Applause is the 1st single from Gaga's ArtPop, out on November 11th!