AdWords Clicks vs. AdSense Impressions

One of my readers sent me an interesting question over the weekend in regards to the relationship between AdWords clicks and AdSense impressions. This is from the context of using AdWords to send traffic to AdSense pages, as is done with AdSense arbitrage. Here's the email:

You have an AdWords campaign directed to a site. You have AdSense ads on the site.

Your CTR rate for AdWords 131 clicks, but your impression total for AdSense for the same site is only 85. (These are actual numbers for today BTW).

Why is that? Certainly my stats show that most visitors only stay on the page for 5 seconds or less, but why does the impression not count? Is it based upon unique visitors vs page reloads? Or could it be that the AdSense ads had not fully displayed themselves before the visitor clicked off?

Some very good questions, and very relevant to the kinds of things I've been talking about lately. Let's start with defining what an AdSense “impression” is.

There are actually two kinds of AdSense impressions: page impressions and ad unit impressions. Page impressions treat all ad units on a page as a single entity, which ad unit impressions consider them separate. Whenever an ad unit is loaded by a browser, then, it counts as an ad unit impression. But only the first ad unit to be loaded counts as a page impression — the other ad units don't increment the page impression count.

When AdSense publishers talk about impressions, they're usually referring to ad unit impressions. That's the default view in the AdSense console, and it's the terminology we're going to use.

If you're sending traffic to a site via AdWords, you'd expect your AdSense impression count to be equal to or greater than the AdWords click count. There are, however, a few reasons why the impressions might be lower:

• The visitor immediately went back to the previous page. This is the most common scenario: the JavaScript that displays the AdSense ads simply doesn't have time to run, hence no impressions get recorded. After clicking an ad, many visitors make a split-second judgment on whether or not to stay on the page. If the page loads too slowly, they'll bail. If the heading doesn't catch their attention or seems unrelated to the ad, they'll bail. This reason alone shows why extra care should be taken to properly craft AdWords landing pages. Otherwise you're just wasting your clicks. I recommend you read a book like AdWords Miracle for tips on what to do here.
• The visitor has an ad blocker. Some people don't like ads and block them using a variety of techniques and/or software. So no impressions get counted.
• The visitor is using an old browser or has turned off JavaScript. This is the least likely scenario, but it's possible.

Invalid clicks are also a possibility, but usually that won't affect the AdSense impression count.

Any solution that depends on JavaScript to count impressions — this includes Google Analytics and various AdSense click detectors — is going to suffer from similar problems and the impressions will always be slightly less than the real impression count. But counting impressions based on server logs — how many times a page has been requested — will over-estimate impressions because it will count crawlers and other non-human visitors. There's no perfect solution, to be quite honest.

Hope that answers the question…

Sponsored Link: Have you bought your copy of Uncommon AdSense yet? If not, check out one of my reader's short review of the book.

Eric Giguere wrote Make Easy Money with Google and Uncommon AdSense. His AdSense blog is a lot of work, but also a lot of fun…

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