For the first time in its 55-year-history , the Billboard Hot 100 will not base its chart on record sales alone, now taking on-board YouTube plays to decide who tops the weekly rundown. The move comes just in time for Baauer's song Harlem Shake, which is expected to make is debut at No.1 this weekend after becoming the latest viral video phenomenon.

The bass heavy hip-hop track got almost no mainstream attention following its release as a free download last May, though its popularity exploded this month after thousands of fans uploaded YouTube videos of themselves dancing along. Around 4,000 Harlem Shake videos are being uploaded each day. "The notion that a song has to sell in order to be a hit feels a little two or three years ago to me," said Billboard's editorial director Bill Werde, "The music business today - much to its credit - has started to learn that there are lots of different ways a song can be a hit, and lots of different ways that the business can benefit from it being a hit."

The change of tact is Billboard's latest step in modernizing the Hot 100, which also now incorporates date from streaming services like Spotify. YouTube is becoming increasingly more relevant in the making of hits - Psy's Gangnam Style, Carly Rae Jepsen's Call me Maybe and Gotye's Somebody That I Used To Know are other tracks owing much of their success to the video sharing website. 

The Harlem Shake's monumental rise up the chart means Macklemore & Ryan Lewis's track Thrift Shop drops to No.2, with 412,000 sales.