Impression and CTR fluctuation

Why the big variations?

[starboy]

My impressions and CTR vary a lot - like +/- 50% - from week to week. I'm not talking day to day variation which is understandable, but large week to week bounces.

Do other AdWords advertisers see this too? Is it unique to AdWords, or does this just reflect overall Internet traffic activity?

Is there a site that reports general Internet traffic levels on a daily basis so I can compare?

[Pengi]

What is the sample size involved? How many Ads? How many impressions? Are you showing on content?

After allowing for the weekly cycle, I tend to see fairly slow changes in may data - e.g. growth from week to week - rather than fluctuations. Obviously there are good and bad weeks, but the difference I see from week to week is very small compared to the difference I see from Saturday to Wednesday.

I have over 1000 ads showing on search and content and currently average about 1400 clicks per day.

I have seens very dramatic changes from the content network occasionally: huge increases in ad impressions for a few days (sadly with bid reductions in the CTR for the Ad concerned). I've always put the cause of this down to a particular Ad appearing on a very popular site for a day or so - hence I'd expect to see spikes associated with this.

[starboy]

Hmmm, interesting. My sample size is smaller - 18,000 impressions per week and 5% CTR, both average numbers that fluctuate 50% up or down, week to week. Showing on search only, not on content.

[Pengi]

I suspect it's to do with the relatively small sample size - I certainly saw a lot more variation in my data when I had a similar number of visitors to you.

At that time my site was growing very fast so any fluctuation from week to week was hidden by the underlying growth.

There have been a couple of Google initiatives recently - such as launching the Quality Score algorithm on the content network - that no doubt causes some changes.