We’ve been tracking a variety of statistics using Facebook’s active user figures as disclosed as part of their Social Ads system. As expected, there has been a good deal of growth in their older users, as is reflected in the chart below. The average age of their US user base is still very young, however, at 22.96 up from 22.28 when we first looked at the data on 11/24/2007.

Users of age 25 and older have increased by 31.7%… but the most striking thing is how far out of alignment comScore’s Media Metrix audience measurement figures are compared to these figures. For January 2008, comScore claimed that Facebook’s 35+ audience was 14.687 million, with about 5.36 million in the 50+ age bracket. I used to work at Nielsen NetRatings and we would sometimes see a 30-40% delta between panel numbers and publishers’ web analytics some of which could be attributed to cookie issues etc etc., BUT THIS is a 10x factor difference (that’s 1000%!) , which is a bit hard to simply dismiss.