Interesting article from RevolutionAnalytics. They published the data broken down per country and interest (books, graphics, meetups etc.) as well as per year. The sample represents millions of R users.
Anyone interested in doing some trend analysis, to identify emerging countries or applications, as well as cross-correlations? Note that small countries/year might need to be aggregated due to small sample size. Not sure how the survey was done, but you can find the details here.
Download the data (Excel spreadsheet).