Agreed, shezbut - I am in a profession that wants hard data based on randomised samples of huge populations, so I was thinking the same thing.

In my country, skin colour and ethnicity are two variables that are not registered in data bases of any kind. There are strict laws against that and exceptions are rare. I think many other European countries have similar laws. So the only way to find out would be by getting permission to make a survey of practitioners and patients. It wouldn't surprise me if something like that had been done, but I wasn't able to find anything in a quick search just now.