Today we introduced a new Quantcast traffic analysis feature. Below the traffic overview section of each profile you can find an analysis of the subdomains for any given site.
The profile lists the top subdomains for the site and the ‘% who Visit’.
Quantcast measures unique visitors to any particular site. If an individual visits Google’s Maps at maps.google.com then they are also counted as having visited google.com. A ‘% who visit’ of 5.8% means that of all the people who visit Google over the course of a month, 5.8% of them visit Google Maps.