I researched the language distribution using the Web of Science. Since your interest was in new content, I restricted the search to the period 1985-2015. The total number of mathematics articles in that database is 882565 for this period. Here is the breakdown by language:

<IMG SRC="http://ilorentz.org/beenakker/MO/language_1985.png"/>

[1985-2015]
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The Web of Science goes back to 1945, so I also made the search for the entire period 1945-2015. That gives a total of 1120170 mathematics articles, with this breakdown by language:

<IMG SRC="http://ilorentz.org/beenakker/MO/language_1945.png"/>

[1945-2015]
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Finally, for the last ten-year period 2005-2015 the breakdown (for a total of 459213 mathematics articles) is 

<IMG SRC="http://ilorentz.org/beenakker/MO/language_2005.png"/>

[2005-2015]
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It is clear that the coverage of Web of Science is not representative for Asia, but for the European languages I would expect it to give a reliable breakdown.