Year	% of tax revenue
1972	3.5005834305717616
1973	5.769230769230769
1974	6.431986093003042
1975	8.948635634028893
1976	15.903307888040713
1977	21.774931381518755
1978	19.51369023293829
1979	19.192094313453538
1980	18.341672623302358
1981	16.29237591188671