If there are 120 million Americans adults online, this survey suggests that 31 million Americans read a political blog at least once a month and 6 million Americans read a political blog at least once a day. This would mean that Instapundit is read by less than 3% of those who read political blogs on a daily basis.

I don’t believe it. I suspect the survey results would be quite different if respondents were informed that the Drudge Report, Slate, Free Republic, Democratic Underground, rushlimbaugh.com, and lucianne.com are not blogs.

More: Sitemeter explains why tracking services often overstate the number of blog readers:

Some ISPs (Internet Service Providers) will change someone’s IP address in the middle of a visit or even on each server page requested. [One] problem that all “log” based tracking systems have is they can’t tell when a visitor’s IP address changes in the middle of a visit. A change in the IP address will cause the log based tracker it think the page views from the new IP address are from another visitor and that’ll cause it to overstate the number of visitors. AOL.COM is one of the big ISPs where their user’s IP address address is constantly changing as they browse your site.