Ad Age have crunched a ton of numbers and put together a detailed infographic that reveals some interesting data about the demographics of the various social media channels.

The emphasis is on Facebook and LinkedIn, but there’s some choice insights about Twitter, too.

Ad Age collected data from actual user profiles (not just web traffic), and determined that:

• Less than 10% of the US population uses Twitter (which matches other studies we’ve seen this year)
• The audience slightly favours women – 54.6% versus 45.4%
• 83.8% of the network are aged between 18-49. In fact, the two demographics used (18-29 and 30-49) are almost identical in size (41.5% vs 42.3%)
• 63.7% of all users are white

From this, we can approximate that if you stumble across a user on Twitter the chances are that they’ll be female, white and aged somewhere between 18-49, or 33.5 years old, given how closely the 18-29 and 30-49 results split down the middle.

Not all that surprising, perhaps. And these results aren’t far off that seen from a different study about a year ago, which suggested that the average Twitter user was a 39-year old woman. Still, interesting as they are, stats and particularly averages should be taken with a good-sized pinch of salt.

Here’s the infographic, which includes some rich data on Facebook, LinkedIn and MySpace (click to enlarge).

(Source: Ad Age.)