On one of my sites with AdSense, I use Slimstat for my visitor tracking to see number of visits, uniques, how they got there, etc. I've noticed a large gap between what it shows as the number of visitors that I have versus what AdSense shows.
I have AdSense ads on every page of this particular site, so my thought is that one visitor viewing one page would generate one page view in Slimstat and one page impression in AdSense. But that's not at all the case. Without giving away my exact page view statistics for September (I'll use a constant "X"), here's what I see:
Slimstat Impressions - 36X
Slimstat Visitors - 19X
AdSense Impressions - 8X
So I have 36 page views for every 19 visitors, which is fine. But I only have 8 page views logged in AdSense for every 36 visitors.
Slimstat has a feature that will allow you to not log search engine crawlers, which is enabled, so they don't skew the results. But I'm not sure how Slimstat does this (I haven't been able to find a list of search engines, user agents, or IP addresses in the software).
I'm wondering if anyone can provide insight as to why this disparity. I've considered the following possibilities:
- Most of the people visiting my site have ad-blocking software that blocks AdSense.
- Slimstat is not able to accurately detect all search engines crawling the site.
The last of those options seems to the most likely to me. And if that's the case, I'd like to know how the software does what it does so I can fix it to bring its numbers and the AdSense numbers more in sync.