Initially identified as the social network for college students, Facebook opened its doors for more and more sections of the population: high school students, then businesses, then everyone in the world. That youthful population that the site began with has gradually been aging because its appeal has been broadening to older groups. As seen by coverage from Inside Facebook, a tracker for the network, developing and marketing platform, the fastest growing demographic is women over 55 with nearly 1.5 million new users over the last 180 days. The last six months has seen the biggest growth in absolute new users amongst users 35-44, with over seven million new users.

Compared to adoption for both 13-17 and 18-25 year olds, where growth was under thirty percent, growth edges up for each older demographic:

26-34 year olds: one hundred percent growth (13.4 million)
45-54 year olds: around 400 percent growth (4.6 million)
55-65 y.o. males: near 425% (1 million), 55-65 y.o. females nearly 550% (1.7 million)

Now that there are so many older members, the majority of US Facebook users are over 25. Even though this 54 percent is a majority, the largest individual demographic is still the 18-25 year olds at 35 percent.

Will young people move on to the next start-up social site, WebProNews wants to know, leaving parents and grandparents to poke and throw sheep at each other? Or will they realize that those folks will just follow them to the new site eventually? It is hard to tell since no previously popular social sites, such as MySpace or its predecessor Friendster, have the broad appeal that Facebook has managed to develop.

Meanwhile marketers are adjusting their strategies to fit with this new data. More opportunities beyond the traditional base of teens and college students provides different types of audience value, acoording to Art Sindlinger, vice president and social activation director at Starcom USA in MediaPost, Friday.

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