Rihanna graced the top of a another Billboard chart this week, but it's not one you have heard of before. Billboard Magazine has debuted a new chart called Social 50 which is determined by an artists' popularity on social networking sites.

The debut chart's Top 5, in order, is composed of Rihanna, Justin Bieber, Eminem, Lady Gaga and Nicki Minaj. The rankings for the weekly chart are based on a formula that includes how many fans the artists official pages have added on Facebook, iLike, MySpace, Twitter and YouTube, and also considers their ratio of page views to fans as well as song plays.

"The Social 50 provides a weekly snapshot of the artists that music fans engage with the most in the social arena, which in today's world is a significant validation of their investment in an act," said Billboard Chart Director Silvio Pietroluongo in a statement.

Billboard will receive the data it uses to determine the chart from Next Big Sound, which tracks music activity on social networks. The Billboard Social 50 Chart will be available every Thursday. Add "make sure you're trending on Twitter" to the promotional itineraries of artist and their labels.

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