I looked at the top 4 performing keywords in an adwords group over time. Over the last month or two I've noticed that the no1 term has slipped down to position 3 in terms of the amount of clicks and the amount of impressions its getting. This would be a pretty significant shift. What could cause this? For instance say 'holidays in Spain' was the best performing broad match keyword in terms of impressions over the last 22 months, why would ‘spanish holidays’ suddenly get the most impressions?
Have you added keywords? Have you added negatives to that group? Did you lower your budget? Did you create other groups? Did you add new ads or pause existing ads? What was your average position and what is it now? Have you noticed your QS going down? What about CTR? Obviously, a lot of things you do yourself will produce different results in impressions, clicks and whatnot to keywords, ads and groups. You also don't live in a vacuum, you have competitors also making changes. Finally, Google is always trying to improve their system. All these will have an effect.
topics hot at the time get more impressions , for instance here in indenpendence day in india , i get more traffic and more money with google because my site is reg that other times , i have to keep quite with my adwords..lolz..