Stats for counting blog visitors and subscribers can be fairly difficult. It's easy to find the amount of normal visitors to your blogs. It's a simple number, the same as any other website you host. But what do those numbers really mean?
Newsreaders Skewing Stats
With the advent of RSS and newsreaders, the number of visitors does not represent the actual amount of time someone spent viewing your blog. This is for two reasons:
1). Newsreaders check your RSS often for updates
Newsreaders usually check an RSS feed every hour or so to see if it's been updated. Once there is an update, it alerts the user. The problem here is that each of these checks counts as a "visit" to your blog rss page. Yet, the user will only actually look at your content when a page updates. You may have hundreds of visits from a user, but only one actual viewing of the content.
2). Some newsreaders aggrigate feeds for multiple users
This is the problem in reverse. Some newsreaders (like Bloglines) pull your RSS feed to their server, then multiple users of that reader pull from the sites news feed.
What this means is you could have hundreds of people viewing your content through sites like Bloglines, yet since Bloglines is the one accessing your account, not the user, it looks as if these hundreds of people are only one person.
Getting a Handle on Stats
To get the actual number of people viewing your site is quite difficult because of the above reasons. Add in the fact that people also use your blog site itself and not just your RSS feed and this complicated matters even more. But there are a couple options on how to guage the traffic on your blog.
Worry about trends more than traffic
Worry less about the actual number of visitors and more about where the trends are headed over time. If you are doubling your number of visitors every month, something must be going right.
If you feel the number of sessions is too sporadic because of the problems with newsreader access, just go by the unique IP numbers. This will in effect count each person on an IP as one person, regardless of the number of times their newsreader accesses your site. It will give you a better idea of the number of people accessing your site.
There are still problems with this approach. Bloglines will still count as one person, even though hundreds are reading it. Large organizations that all come from the same IP (such as the Walker) will count as one user, even though multiple people may be subscribed to your feed.
Stats hacks can help (some)
You can also change your stats package to target just the RSS feed, to find the number of subscribers via unique IP. Bloglines also sends how many people are subscribed to your feed in their headers when they spider, and although no stats program uses that information, a clever hack in the stats program could add this info to the mix.
This is not an optimal solution because it requires a fair amount of work and rewriting software, which not everyone can do. But it is another way to being more exact in your findings, should you chose to go that route.