This Week in Social Analytics on Tumblr | From ComScore’s 2013 U.S. Digital Future in Focus:

“Three social networks in particular – Tumblr, Pinterest and Instagram – each gained more than 10 million visitors over the course of the year in part by catering to a desire for more visually appealing content. comScore has called this phenomenon “the rise of the visual web.” Of the three, Tumblr had the largest audience at 30.8 million visitors (up 64 percent from the prior year), while Pinterest (up 284 percent to 28.9 million visitors) and Instagram (up 284 percent to 27.4 million visitors) both shared the same outsized growth rate.” 

The first graph above shows the shares for time spent on each site, with Tumblr coming in second behind Facebook, while the second shows the total unique visitor trend with Tumblr trending above both Pinterest and Instagram. 

You can download the full report at the link at the top of this post.