According to data from web measurement firm Quantcast, Tumblr's getting ready to wrap up a year of major traffic growth. A Tumblr blog post is claiming that the site is now one of the top ten most-visited sites in the US and that it has a worldwide audience of 170 million people. Tumblr's reaching a bit — the latest Quantcast monthly data actually shows worldwide traffic of 168 million users in the last 30 days, but it's nonetheless a big jump from the 120 million monthly users (again, according to Quantcast) that it hit back in January of this year. It's worth noting, however, that while Quantcast has a number of major partners (including Tumblr) who include the Quantcast site traffic coding on all of their webpages, the vast majority of its traffic data are projections and estimates. So while Quantcast may show Tumblr to be a top-ten site, other web measurement firms (like ComScore) could show different data.
Regardless of data methodology, Tumblr is certainly having a big growth year with lots of highs and lows — the highlights included the microblogging service's role in the meme-ification of this year's presidential elections and its continued efforts to improve its mobile experience (which included a new photo-sharing app for iOS users). On the downside, Tumblr gets hit with major outages more than users would like, and Twitter blocked users from using it to find friends on the Tumblr platform. Still, it seems the good outweighs the bad for the denizens of the internet — according to Quantcast, Tumblr's traffic has increased almost every month for nearly four years.