My impression is that most math papers (and almost all of the most important ones) are now published in English. Not long ago (historically) publishing in French, German, Russian, etc. were more common. I'm curious when and how this transition occurred, and what it looked like while it was happening.
Of course English is the dominant language for many other areas such as publications in the sciences in general, international business, the internet, etc. Nonetheless I have the impression that the transition occurred later and more slowly in math than in some of these other areas. This may be false; I don't know why I think this.
Perhaps I have this idea because math graduate programs are unique among technical fields in having a language requirement, though that could also be explained by our tendency to read more old papers than say, biologists. But it seems plausible that the transition would occur later in math because math can be more easily undertaken as a solitary activity than the sciences.
My main question is: where would I find data on the representation of different languages in papers in top math journals as, say, a fraction of total papers? Of course I could try to determine what the top journals were at various times and go through their tables of contents for each issue and compile such data myself. But it seems plausible someone may have already done a study of this and in much more depth than I would have time to do by myself.
Secondarily, perhaps there are published anecdotal accounts about how and when this transition occurred? I can imagine there may have been resistance by some. It may have happened at different times in different subfields for different reasons. Perhaps some landmark papers in English paved the way.
I would be grateful for pointers to literature examining any of these issues. Comparisons with other fields such as physics would also be interesting, but I'm primarily interested in math.
Best Answer
Now that the texts of all of the Plenary talks at the international congresses of mathematicians is available online, that could serve as a data source for the transition. This year, every plenary talk was in English, and none of the speakers (that I attended) were at all difficult to understand, at least not on account of the language.
Here are some years, and the number of Invited plenary Speakers whose title is in (English, French, German, Russian).
1920: ( 2, 3, 0, 0), in Strasbourg
1932: ( 2, 9, 9, 1), in Zurich
1936: ( 7, 2,12, 0), in Oslo
1950: (19, 2, 1, 0), in Cambridge
1954: (14, 3, 2, 1), in Amsterdam
1958: (13, 3, 2, 1), in Edinburgh
1962: ( 9, 3, 1, 3), in Stockholm
1966: ( 9, 1, 2, 5), in Moscow
1970: (15, 1, 0, 0), in Nice
1974: (15, 2, 0, 0), in Vancouver
1978: (17, 0, 0, 0), in Helsinki
1983: (12, 0, 0, 0), in Warsaw
1986: (13, 0, 1, 1), in Berkeley
1994: (14, 0, 0, 0), in Zurich
1998: (15, 0, 0, 0), in Kyoto
2002: (19, 1, 0, 0), in Beijing
2006: (19, 0, 0, 0), in Madrid
So the supposition that World War II is the cause isn't supported by this data. Certainly it impacted the use of German, but other languages were common until the 1970s. Something drastic seems to have happened between 1966 and 1970.