The table below indicates that the 60 known, largest Deep-Web™ sites contain data of about 750 terabytes (HTML included basis), or roughly 40 times the size of the known surface Web. These sites appear in a broad array of domains from science to law to images and commerce. We estimate the total number of records or documents within this group to be about 85 billion.
By nature, this listing is preliminary and likely incomplete, since we lack a complete census of Deep-Web sites. This inability today to identify all of the largest Deep-Web sites should not be surprising. The awareness of the Deep-Web is a new phenomenon and has received little attention.