Billboard has launched a new chart tracking musicians' popularity across social-networking sites. The chart, dubbed the Social 50, rounds out the data supplied by the magazine's rundowns of the most popular albums and songs on radio playlists and at record stores across the U.S.

Topping the inaugural edition of the Social 50 is Rihanna, who had the highest number of new fans, unique pageviews and song streams on Facebook, iLike, MySpace, Twitter and YouTube for the chart week of December 11. Rihanna has two songs in the top 10 of the just-released Billboard Hot 100; "Only Girl (In The World)," which topped the chart last week, is at Number 3, while the Drake-assisted "What's My Name" has risen to Number 5.

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The top five of the Social 50 is rounded out by Justin Bieber, Eminem, Lady Gaga and Nicki Minaj. Among the data used to calculate the chart's outcome is a ratio that measures pageviews against the number of fans; Bieber is leading the pack in total pageviews for the week, while Rihanna outstrips her rivals in the adding-fans category.

A similar effort to incorporate online data into the pop charts was undertaken earlier this year by the media-measurement company BigChampagne, which launched the Ultimate Chart last summer. In contrast to the Social 50, the Ultimate Chart combines data from streaming-media sites like Vevo, MySpace and MTV.com with sales and playlist data. On the current edition of that chart, Rihanna is the top artist, while Ke$ha's "We R Who We R" is the Number One song.

Social 50 [Billboard]

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