The circles above roughly represent the sizes of U.S. Facebook audiences addressable by the various targeting criteria available to advertisers.  Working from the outside in, we have gender, age, relationship status, education, and workplace.

As you can see, just about everyone on Facebook is reachable by gender and age criteria, while only very few people are reachable by workplace.  More interesting than the absolute numbers, though, is why the circles above are roughly concentric.  Information on Facebook is sticky; the more a user shares one thing, no matter what it is, the more likely that user is to share other things.  For example, a user who shares information about their workplace on Facebook is 24% more likely to share a relationship status than an average Facebook user.  More broadly, women have higher propensity to share information than men, and younger users have a higher propensity to share than older users.  In fact, a 14 year-old is twice as likely as a 45 year-old to Like something on Facebook.

Facebook Wins in ‘Targetability’ Comparison with Traditional Display Advertising

XA.net has served over 70 billion display ads in the last three years, and we work closely with a variety of data providers and ad exchanges to figure out the best targeting available to advertisers and agencies. When it comes to comparing the availability of the biggest sets of targeting data, age and gender, Facebook wins by a country mile.

The US total internet audience is about 215 million people, according to comScore (July 2011 dataset). At best, via third-party data one can see age and gender estimates on 40% of that audience, or about 86 million Americans. Compare that to (again quoting comScore data) Facebook’s 162.1 million users x 95% = 154.0 million users. Facebook wins by a staggering 79%! It’s not even close. Note too that the accuracy of data provided by third parties like TargusINFO, BlueKai, eXelate and so on is probably weaker but certainly no better than that of Facebook’s. Here’s a chart that shows these figures graphically. (user figures in ’000′s)