http://awstats.sourceforge.net/docs/awstats_glossary.html Add To Favourites: This value, available in the "miscellanous chart", reports an estimated indicator that can be used to have an idea of the number of times a visitor has added your web site into its favourite bookmarks. The technical rules for that is the following formula: Number of Add to Favourites = round((x+y) / r) where x = Number of hits made by IE browsers for "/anydir/favicon.ico", with a referer field not defined, and with no 404 error code y = Number of hits made by IE browsers for "/favicon.ico", with a referer field not defined, with or without 404 error code r = Ratio of hits made by IE browsers compared to hits made by all browsers (r <= 1) As you can see in formula, only IE is used to count reliable "add", the "Add to favourites" for other browsers are estimated using ratio of other browsers usage compared to ratio of IE usage. The reason is that only IE do a hit on favicon.ico nearly ONLY when a user add the page to its favourites. The other browsers make often hits on this file also for other reasons so we can't count one "hit" as one "add" since it might be a hit for another reason. AWStats differentiate also hits with error and not to avoid counting multiple hits made recursively in upper path when favicon.ico file is not found in deeper directory of path. Note that this number is just an indicator that is in most case higher than true value. The reason is that even IE browser sometimes make hit on favicon without an "Add to favourites" action by a user.
I would say not very.... From my AWSTATS: Add to favorites (estimated) 5618 / 3859 Visitors 145.5 % Kind of hard to imagine more people adding my site to their favorites than have actually visted the site
Repeated visitor would be better measure. I have : 153 / 852 Visitors 17.9 % which I found unbealivably high.