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I agree that you're probably not going to find these rates except through the individual EU Competent Authorities. NBs don't publish this data (I'm not sure of the exact reason, but the first thing that comes to mind is that it could imply the duty of confidentiality we have). But the Competent Authorities could have data on the numbers of new devices registered in the country each year, which could indicate the numbers of devices that gain CE marking that year. Make sure to check more than one competent authority to get a more accurate number, since sometimes manufacturers decide (for various reasons) register their device in one country, but not another.
Hope this helps!
Hope this helps!