Video hasn't killed radio, but it's certainly moving into its territory now that the Billboard Hot 100,  magazine's top singles chart, has begun factoring YouTube plays of songs into its formula for rankings.

Tracked by the ratings service Nielsen, the top songs chart was previously ranked by digital download and physical singles sales, radio airplay, online audio streaming and online radio streaming.

The new system began this week, giving way to viral video phenomena like Baauer's "Harlem Shake" and PSY's "Gangnam Style" to bubble to the top, regardless of radio-play.

"The very definition of what it means to have a hit is ever-changing these days,” Bill Werde, Billboard’s editorial director, said in a statement. “When the charts launched over 70 years ago, a hit was defined as selling copies of a single or generating airplay. While those avenues are still viable, one needn't look any further than Cee Lo, Gotye, PSY or now Baauer to know that a song can be a massive hit on YouTube alone."

Billboard will incorporate all official videos on YouTube captured by Nielsen's measurement, including Vevo on YouTube and user-generated clips that use authorized audio.

While "Harlem Shake" will rise to No. 1 this week, other highlights getting a bump from YouTube plays include Rihanna's 3.8 million-views hit "Stay" and Drake's "Started From the Bottom," with its nearly 5.1 million views.