We all know AdSense is very smart. It can detects the language of website then deliver ads with right language. Many people would ask that is language very important to the revenue of AdSense? since ads in different language target different visitors who come from different countries.
I also wondered this question in the past, and I even heard that AdSense in English normally gets higher “cost per click”, because they are usually clicked by viewers from Europe and North America. But I doubt the conclusion.
Fortunately, I have two websites with two completely different languages, i.e. English and Chinese. The former one focus on a very narrow topic: cement, it is a kind of niche blog. The latter is a blog about every thing I think worth blogging. Both of them are placed with AdSense at the same position.
What is the result? There is hardly difference in terms of “cost per click” and “Page CTR” over all of time in this year. The only difference is that the website in English got slightly higher cost per click, but the difference could be caused by the niche content which can match the right ads better than the other.
My personal “experiment” is that language of AdSense has nothing to do with “cost per click”. I think the most important is the geological location of the readers who might click AdSense ads, since the ads from developed countries usually have higher budget compared with their counterparts in developing countries, regardless of what language they use.
Of course, as for the revenue of Adsense, language may play an important role, for example, the audience in non-English in United States is much smaller than Chinese, which means traffic in Chinese is probably much less than English, and thus less clicks, though the “cost per click” is not changed. However, you may also get more traffic because the competition in Chinese is also much less intense than English.
Anyway, to make more money with AdSense, the key point is creating great content for your readers. If there is another trick, that is targeting readers from developed countries, even they may not use the dominated language of the place.