[UPDATE September 07, 2014] With Kei Nishikori and Marin Cilic reaching the 2014 US Open final, it is clear that this article needs updating. I will do so after the end of the 2014 season, when the ATP and WTA publish their updated rankings.
Men are from Spain, women are from Russia
After spending four full days on the grounds of the Billie Jean King National Tennis Center on the eve of the 2012 US Open tennis tournament, I decided to put together two simple maps showing where the world’s top professional tennis players come from. According to the August 20, 2012 rankings of the WTA and the ATP, the most female players in the top 100 come from Russia (10), the most men from Spain (12). The US has eight women and nine men in the top 100.
Below each map is a link to a table (Google Docs, no login required) showing the data used in that map.
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No women from Latin America, no men from China
[UPDATE 08/26/2012] I superimposed both maps to create a third, composite map of all 200 top professional tennis players (by country).