One way to monitor the degree of adoption of the Semantic Web is to estimate the number of Semantic Web Documents (SWDs) accessible on the Web. Jim Hendler asks, How many OWL ontologies are there on the Web? in an interesting post and he describes how he’s tried to estimate this using Google.
When Li Ding tried to do this recently as part of his dissertation, he came up with an estimate of between 10**7 and 10**9 documents. The upper bound is surely loose, but I think an estimate of five to ten million SWDs is quite reasonable. Here’s how we came up with this estimate.