Three plants produced 94 percent of Germany's synthetic rubber. Two plants produced four fifths of the cyanide used to make airplane Plexiglas. One plant made four fifths of the bydrazine hydrate used as a rocket and V-weapon propellant. And one plant made virtually all of the elemental phosphorus needed for tracer bullets and chemical warfare.
The Integration of the German Oil, Chemical, Rubber and Explosives Industries
Check the chart on effect of the bombing of the oil industry below. As the text says " The first two months of strategic bombing undid the results of three years strenuous work by the Germans." IŽd say the result seems quite effective although I know that you can use charts to "prove anything"...
http://www.sturmvogel.orbat.com/images/ussbs/fig12.gif