“Nielsen’s online data shows that about half of the U.S. population visited a social networking website in the last year and that number grows every quarter,” said Wils Corrigan, AVP, Research & Development, Nielsen Claritas. “The rising popularity of these sites and the deep engagement consumers have with them has advertisers and marketers asking for more and more detail as to which lifestyles should be targeted for their online advertising and promotions.”

Facebook vs Myspace

Through Claritas, Nielsen defines U.S. households in terms of 66 demographically and behaviorally distinct segments like “Young Digerati” or “Beltway Boomers.” When those segments are overlaid with the activity of Nielsen’s online panel of more than 200K, we see a marked difference in the demographic makeup of the two largest social networks, Facebook and MySpace.

• Facebook users have a largely upscale profile. The top third of lifestyle segments relative to affluence were 25% more likely to use Facebook than those in the lower third.
• The bottom third segments related to affluence are 37% more likely to use MySpace than those in the top third.
• Users of Facebook were also much more likely to use LinkedIn, a network geared towards business and professional networking, than those who use MySpace.

Bloggers more urban as well

According to Nielsen Claritas, the blogging and tweeting community at large isn’t necessarily more affluent, but bloggers and tweeters do live in more urban areas such as New York, Los Angeles, San Francisco, and Chicago. The penetration rates of the top two most visited blogging platforms (Blogger, Wordpress) and the most popular micro-blogging platform (Twitter) show that Nielsen’s 12 Urban lifestyle segments are more likely to blog and tweet than Nielsen’s 22 Town & Rural segments.

Not surprisingly those lifestyle segments most likely to blog and tweet also tend to use Facebook and LinkedIn more often than those segments that typically don’t blog or tweet. Case in point, the Urban lifestyle segments for Blogger are 18% more likely to be Facebook users and 140% more likely to be LinkedIn users than the below average segments.

About the methodology

Nielsen examined the seven most-visited social networking websites and platforms: Facebook, MySpace, Blogger, Twitter, WordPress, ClassmatesOnline, and LinkedIn. Website penetration by segment was calculated by dividing the number of unique visitors to the website per segment by the total number of households in each segment.

Nearly half of the biggest social networking sites are also among the fastest growing, according to data released Wednesday by Nielsen Online.

These top sites have also expanded beyond the youthful audience the social networking space initially captured — to find a place in older visitors’ professional lives.  Facebook, LinkedIn, and Reunion.com are most popular among visitors ages 25-34, 35-49, and 55-64, respectively, Nielsen reported.

View the full press release.

Read coverage of Nielsen’s findings in Media Post, Wired, and PC Magazine.