Tumblr Hits 13.4 Million Visitors in July; Grows 218% Year Over Year

New data from comScore shows that micro-blogging platform Tumblr has experienced significant growth over the past year, with visitor numbers growing from 4.2 million in July 2010 to 13.4 million in July 2011, up 218%.  Tumblr’s demographic is heavily skewed toward younger generations, with 50% of the site’s visitors under age 25.

Tumblr Grows 218 Percent in One YearUser growth accelerated over the last few months, with a jump of 5 million additional visitors from April through July.  The comScore blog attributes this to Tumblr’s reaching “the benefits of the network effect.” This is based on the idea that social networks become more valuable to users when there are more users on the network; and at that point, users continually encourage new members to join.

Once this effect has taken hold and a social network achieves “critical mass,” then “adoption tends to accelerate.”

Tumblr Demographics: Half of Visitors Are Under Age 25 via comScoreThe comScore data lays out the age composition of Tumblr’s userbase, showing the platform’s popularity among teens and college-age users: teens ages 12-17 and users ages 18-24 are twice as likely to use Tumblr as the average Internet user.  The number of Tumblr users drops well below the number of total internet users for all age groups 35 and over.

As Tumblr starts to see the benefits of “the network effect,” will the site begin to reach an older demographic in significant numbers?