I’ve been trying to get a handle on the demographics for Facebook and MySpace to help a client decide which best fits his target audience. This has not been easy.

This chart from iStrategyLabs, was published October 22, 2007, and, according to the company, comes directly from Facebook Ads.

This chart indicates that the largest demographic is 18 to 24 with nearly 62%, and the 35+ segment commands less than 5% or less than 1 million users. (I believe the three categories at the bottom of the chart are supposed to read “Sex, Drugs and Rock and Roll.”)

The following chart from comScore indicates the largest Facebook segment is 35+, with 10,412 million “visitors.”

While the chart is for May 2007, it is the most recent I can find on their site for this particular statistic.

The difference between the two charts may be terminology, but I’m not sure that can account for the disparity. The comScore chart says “visitors,” which could mean multiple visits by the same member, whereas iStrategy/Facebook says “users” which sounds like registered users. Also, the iStrategy chart is U.S. only and the comScore appears to be worldwide.

I contacted Facebook and asked them to explain the difference, and they responded “As you select your targeting criteria for your ads, we will display the approximate number of users that your targeting encompasses. Please keep in mind that this estimate is not exact and that your ad may not be shown to every one of these users depending on what other ads are available to show.”

I have yet to try this, but will be curious to see how it tracks to either of these sets of figures.

Tags: Facebook, iStrategy Labs, Facebook Ads, comScore, demographics