I am studying World War One and our textbook says that there were certain "starred" occupations that were very important for the war effort and could excuse you from service, but does not really go into detail. I would be interested to know what these occupations were. Our book also only really goes into detail about the situation in Britain and so I would also be very interested to know if there was a German equivalent of this and whether or not it was more or less successful than in Britain.
I don't know what the situation was in Germany, but I know that in both France and Britain, there were certain occupational categories that were exempt from being drafted, as they were considered critical to the war effort. These included: some kinds of shipyard workers, especially welders; munitions factory workers, especially machinists and tool-and-die makers. I think some kinds of mine workers were also exempt from being drafted, again, the idea being that their work on the "home front" was equally critical to victory as that of a soldier holding a gun.