netmeg - 12:41 pm on Aug 20, 2012 (gmt 0)
If it is in my power to change things, then I will, if it is some weird stuff Google has put in place, then there is nothing I can do and I will just have to find a new way to make up for that 25%.
You can test different placements and ad styles, you can add more sites (or places to put your ads) and you can add new content (although with IBA the percentage of ads related to your sites's content is probably lower than it was) but that's about it. The rest is pretty much Google's black box.
Other things that could have happened include advertisers that you had previously dropping out, running out of budget, getting kicked out of AdWords, or deciding for whatever reason they didn't want to run ads on your site and blocking it.
You don't say how long your site(s) has been up, but it's also possible that smart pricing has just adjusted itself.
If I were you, I would probably next do some analysis on my traffic - is it pretty stable? Is it coming from the same places it always has, or are there spikes from unlikely referrers or countries? Is your search traffic coming in on the keywords you'd expect them to? I'd go back at least to the beginning of the year, and look for patterns. There *is* a traffic quality element that kicks in, so if anything has changed there, you should be aware.