A Google Groups thread asks the question on why when a advertisers sets his AdWords campaigns to “Rotate: Show ads more evenly” in the campaign settings, does it not always rotate 100% evenly?

The advertiser asked:

AdWordsPro Steph said that there are other factors involved when it comes to when ads are rotated evenly. Here are some reasons why an ad may not be served evenly with others:

Forum discussion at Google Groups.