Our first statistical measure is simply the rate of document access. This rate depends on a large number of extrinsic factors, including the size and health of the field to which the document refers, the amount of advertising, the level of net-consciousness of the community, and so on. The interest here lies not so much in the absolute rate of access but in the time course of this rate. This time course should be more revealing of the intrinsic qualities of the document.
Popularity is easy to measure.
It is simply the number of times a document has been visited. In the case of ftp downloads, retrieval of a multi-part document counts as one access. The data are shown in figure 1. Both documents seem to be accessed at a nearly constant rate via the web.