How can I check regional popularity of Yahoo?

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In some countries, Google is the most popular search engine, and in others, Yahoo is much more popular. Is there any way to get any statistics regarding how many people use Google and Yahoo respectively in different countries? (I need this info for some research I am doing, and I can't seem to find it anywhere!) I am interested in different European countries mostly, such as Scandinavia, Germany and France, for instance. Do you know of any tool or site that states this?