In late April (after studying the available 4 week of data - and years of 'gut feeling') I reduced the number of countries being shown Adsense ads on my site down from a daily average of 179 countries down to just 17 of the best converting/traffic countries (mainly English speaking countries or English as a dominant second language - and no Belgium did not make the cut).
Reasons For This: I just cannot see Adsense having the inventory for so many countries, especially in the developing nations - the market needs time to mature. Also not one of my direct advertisers ever asks to target more than 5 or 6 countries at most - i.e. not one brand has ever asked for global ad impressions when given the choice to target individual countries. These countries are the English speaking nations, targeted by my website, so I am not sure how Adsense ads could ever really benefit readers outside of this narrow targeted country and language range using contextual advertisements.
Note: that is NOT to say my website information will not benefit people outside of the English speaking nations ... Previous CTR data seems to bare this out. For many of the developing nations, certainly those with a
consistent zero CTR, this says either the demand/incentive to click on Ads or Ad inventory itself is lacking in Adsense for these countries (at least in my niche, YMMV). I have also cut out many 'foreign language' developed countries from the EU who also do not click on ads from my site; not sure 'why' these visitors do not click, apart from poor ad targeting (?) but see below for an unintended consequence in improved visitor experience for these visitors.
Last week I further reduced it down from 17 to just 11 top performing countries. And I am happy with the results having done so. Impressions are down, but CTR is up (no surprise there, there is a correlation when you narrow the focus) but other metrics have also improved, and overall income is up (
YMMV so test, test and test some more, what is good for my site may not be good for yours).
Plan of action - I will always keep the top 9 countries of the 11 but I will rotate out two of the least performing countries of the 11 every month, and replace them with two others for a month (from my previous top 21 which I have on record) to see how they fair. Then rotate out the bottom 2 performers and try them with another two different countries etc. This is to make sure I have not excluded a country that could perform better in the future.
Unintended Consequences - in WebmasterTools the overall average site speed has decreased (yes, I am aware of how it is measured). Countries outside my top 11 are having the same access to information on my site, just without Adsense ads (or direct Ads) being shown to them, (perhaps this is a better user experience) and this is saving over 2 seconds on average with each page load.
For my English speaking targeted countries, with a broadband internet infrastructure, page load is not really an issue, but for poorer, developing nations, without broadband infrastructure, it seems the pages load much quicker without the ads, and bounce rate is reduced for these nations (and also for foreign language visitors from developed countries, which also do not get shown ads) ... <educated-guess> an improved overall user experience and lower page loads speeds may help in future SERP's(?) I repeat '
may' help - it can't harm </educated-guess>
FYI ... The new tool in webmaster tools which 'previews' the site shows the site without ads, i.e. it shows the site as other countries outside the top 11 see it. Therefore I have used collapsible <div> boxes to show the ads (width is given in the CSS but no height) which then 'disappear' without the ads in them, collapsing the space into which other information boxes shift - making the site very presentable when ads are not shown.
Caveat: you cannot target adsense to specific countries using the adsense tools given in the adsense manager - you need to use internal server side scripts or a third party ad manager.
