Alexa has improved a lot than what it was before in ranking sites. Before Alexa used to rank websites just based on alexa toolbar users. Now the criteria for ranking has changed they have tie up with other ranking companies and they use their own toolbar data with other company data to decide the final rankings. Still I feel alexa rankings are skewed and influenced more by toolbar related factors.
Well here the question whether Alexa sees sub domain as a separate entity to rank it? In most cases no alexa rarely sees separate sub domains as a different entity. I have seen BlogSpot domains having Alexa rank of 500. The 500 is not for BlogSpot sub domain but the usage of blogspot.com itself.
A word from the official Alexa blog:
Alexa’s traffic rankings are for top level domains only (e.g. domain.com). We do not provide separate rankings for subpages within a domain (e.g. domain.com/subpage.html) or sub domains (e.g. subdomain.domain.com) unless we are able to automatically identify them as personal home pages or blogs, like those hosted on Geocities and Tripod. If a site is identified as a personal home page or blog, its traffic ranking will have an asterisk (*) next to it: Personal Page Avg. Traffic Rank: 3,456*. Personal pages are ranked on the same scale as a regular domain, so a personal page ranked 3,456* is the 3,456th most popular page among Alexa users.
So they don’t separate if the don’t identify them automatically. They have such a dumb automated algorithm and it never detects proper sub domains. I feel Alexa need to improve their algorithm on working with sub domains because sub domains are actually different websites.Visit www.searchenginegenie.com for more interesting blogs on Search engine related information