How much of the web is archived?

The Memento Project's archive access additions to HTTP have enabled development of new web archive access user interfaces. After experiencing this web time travel, the in- evitable question that comes to mind is "How much of the Web is archived?" This question is studied by approximating the Web via sampling URIs from DMOZ, Delicious, Bitly, and search engine indexes and measuring number of archive copies available in various public web archives. The results indicate that 35%-90% of URIs have at least one archived copy, 17%-49% have two to five copies, 1%-8% have six to ten copies, and 8%-63% at least ten copies. The number of URI copies varies as a function of time, but only 14.6-31.3% of URIs are archived more than once per month.