The Latest Numbers on Facebook's September US Traffic from comScore, Quantcast, & Compete

ComScore, Quantcast, and Compete have all just released their September numbers, so here’s the latest look at Facebook’s US traffic according to each metrics firm. As always, it’s important to note that these services often differ from one another because each service uses different methodologies with different strengths and weaknesses – usually based on some combination of self reporting, ISP reporting, and panel sampling – but together, we can use them to triangulate trends in Facebook’s US traffic.