Membership of virtual worlds grew by 39% in Q2 2009

"The consultancy kzero.co.uk reports that membership of virtual worlds grew by 39% in the second quarter of 2009 to an estimated 579 million."
Source: Kzero, quoted by The Guardian, 29th July 2009
More data:
"Almost all of the 39% growth came from children. Girls used to grow up with their dolls; now they are growing up with their avatars. This goes largely unreported because the users don't read newspapers, but as Kzero reports, poptropica.com – aimed at five- to 10-year-olds – has 76 million registered users. If you move up to 10- to 15-year-olds, users rival the populations of countries – led by Habbo (135 million), Neopets (54 million), Star Dolls (34 million) and Club Penguin (28 million). It starts tailing off among 15- to 25-year-olds – apart from Poptropica (35 million) – but it underlines the likelihood that as youngsters get older they will be looking for more sophisticated outlets and for ways to link existing social networks such as Facebook or MySpace to more immersive virtual worlds."