Yahoo’s $1.1 billion acquisition of Tumblr may have saddled the still-troubled Internet giant with a wasting asset, Buzzfeed reports. Traffic figures supposedly “directly measured” by Quantcast show that monthly unique visitors to Tumblr peaked last November; a more abbreviated chart of weekly unique visitors shows that number falling since May 20.

Tumblr responded that Quantcast doesn’t measure traffic from the Tumblr mobile app, but declined to say whether including mobile-app users would show overall growth. So Buzzfeed looked at data from its own network of sites and found what John Herrman called a “fairly serious decline in Tumblr referrals” (see chart below). Which is interesting, if still not quite conclusive.

Image via Buzzfeed