What do your Ping followers say about an artist's fans and the formats they buy? Billboard analyzed the number of Ping followers for 49 artists and compared them to three metrics for each artist - CD sales, digital albums sales and digital tracks sales from the artist’s most recent studio album, according to Nielsen SoundScan.

The results showed that digital album sales were most highly correlated with Ping followers. (Correlation is a measure of the relationship between variables. The correlation coefficient is 0.66, which shows a fairly highly correlated relationship. Digital tracks (0.55) and CDs (0.5) are less correlated with the number of an artist’s Ping followers.)

What this means in this case is the manner in which iTunes users have selected artists to follow on Ping is most closely linked to digital album sales. There is less rhyme or reason to Ping followers when looking at CD sales and track sales. Of course, this is not surprising as “following” an artist on Ping is to begin a social networking relationship. The person who buys a digital album is more likely to be a fan and want a deeper relationship with the artist than the consumers who buys a hit digital track (a more passive relationship). CD sales’ lower correlation is understandable given it is a physical format and iTunes is a wholly digital experience.

Take out a couple oddities and the correlation actually rises to 0.67. The last studio album of some artists in the sample had more success outside of traditional retail channels. Radiohead’s album In Rainbows has done well at retail but was originally given away at the band’s website through a pay-what-you-want scheme. Nine Inch Nails’ last album, “The Slip,” was first given away for free at the Nine Inch Nails website and released under a Creative Commons license. By the time “The Slip” was available in physical version, it had been downloaded over two millions times.