page impressions VS page views

shouldn't they be equal?

[Perfection]

I've been using 1 ad unit on my site for quite a while now, and I've noticed that over the last 2 weeks only, my daily adsense page impression's number has decreased by a few 1000 (revenue decreased too), while my site's actual number of daily page views remains the same.

Correct me if I'm wrong, but shouldn't those 2 numbers be pretty much equal?

If I have only 1 ad unit on every page of the site, it should mean that for every page that is "viewed," an ad is "impressed." ...right?

I've never actually thought to compare these 2 numbers before, but now it sort of dawned on me.

So, if all of the assumptions I've made in this post are correct, does that mean there is some type of adsense reporting problem here?

[astro_miner]

Adsense may not have ads to show to some of your visitors, perhaps because of geotargetting or low ad inventory in your niche.

Some of your visitors may have javascript off and thereby generate no impressions.

You can specify an alternate page that gets called every time there's no ad to show, and an iframed page inside <NOSCRIPT> tags right after the adsense code. Add up the number of hits on that and the adsense impressions and you should get a number closer to your real pageviews.

[Perfection]

Thanks for the reply. The thing is though, I've been using adsense on this site for over a year now. This decrease in ad impressions started just 2 weeks ago, yet my site's traffic remains the same.

Why the sudden change?

[ann]

could be people are getting more savvy about turning off JavaScript.

[astro_miner]

Maybe the NY Times or their local newspaper ran an article on the Adblock extension for firefox... :)

[bumpski]

I wonder if Google is running into problems with ISP's caching the Adsense javascript (even though it is properly flagged to not be cached). This script is identical for all Adsense publishers so it is highly likely that it is sitting in many ISP's caches. This adsense script may have some accounting weaknesses perhaps affecting Pageviews.
I see lots of evidence of apparent caching of my website(s) pages by many large ISP's even though I have flagged them as not cacheable.
ISP caches can cause all sorts of Page View accounting problems, you may be getting more Page Views of your content than you think. You would think that Google would have a higher and perhaps more accurate value than your web host stats, but it appears Google filters a lot of views, like any duplicate view from the same user.
The Google stats for me usually fall in between unique visits and Page views, which is I guess what I'd expect. With ISP caching who knows what will happen!